Solo Mid-Lane Carry Io Guide (7.06 and above)

Intro

So why listen to me? What makes me an expert on Io?

I have 7750+ matches played in Dota 2, totaling 6700+ hours. Of those ~7750 matches, ~2100 of them have been with Io. This means I have spent more than 25% of my Dota 2 experience playing Io.

I maintain a >55% Io win rate, which is almost 20% above the global average.

I have written an all-round guide to Support Io on Dotafire, which has lots of positive feedback and nearly 10,000 views, available here: http://www.dotafire.com/dota-2/guide/the-1000-commend-io-guide-7-04-and-above-26120

I also manage a small youtube channel dedicated solely to Io gameplay.

The logic of Io as a carry is that he is able to damage himself, via Overcharge and Armlet of Mordiggian, in order to massively increase his melee damage output. Alongside his incredibly strong damage spell Spirits, this allows Io to shred his opponents during the early and mid game, allowing the purchase of some big items to carry through the endgame.

I am happy to admit that I am far more practiced as Io Support than I am Io Carry. That being said, I have worked hard since the 7.00 patch to perfect a mid-lane Io build, and this is it.

If you have any doubts about the viability of this build, watch the videos posted above.

Items (Early and Mid-Game)

In this chapter, I will defend and explain my item choices as presented above.

OPENING ITEMS
Bracer
Bracer provides stats that allow Io to secure last hits, including +6 Str, +3 Int, +3 Agi, and +3 damage (totaling +9 damage boost).
Iron Branch
These provide +1 All Stats (+1 damage and 20 HP). Io does not build any items that require Iron Branch, so this can be eaten with Tangos to extend your health regen in the early game.
Faerie Fire
Provides +2 damage, ensuring further last hit domination, and can be eaten in a tight spot to gain 75 HP.

Receive 2 Tangos from your team supports, as a standard mid would receive.

The logic here is that Io needs as much bonus damage from his opening items as possible to control last hits against heavy-hitting mid heroes like Invoker, Shadow Fiend, and Puck. Io gains +12 damage from these opening items and will enter mid lane with 59 melee damage.

BASIC ITEMS
Bottle
Bottle is a standard mid-lane item that serves to heal HP and MP. It supplements Io's mana, allowing him to abuse Spirits early in the game to harass your mid-lane opponent. Controlling and bottling runes is very important for a successful Io mid!

Blades of Attack
Io needs more damage to ensure he is controlling last hits in the mid lane. Blades of Attack will build into Armlet of Mordiggian later in the game, but are useful now for the +9 damage they provide for relatively cheap cost.

Infused Raindrops
These provide Io magic damage block that will help against almost all mid players, including ganks from supports. Make sure to save 1 Infused Raindrop in your backpack to build into Urn of Shadows later in the game.

Boots of Speed
Self-explanatory. Power Treads are not purchased at this point because (1) the items that form Armlet allow Io to secure last hits easier than Treads and (2) an increase in Io's attack speed (and a stat boost) is more effective once Armlet has been completed.

Boots of Speed can be postponed until after Armlet if you feel you do not need them in the lane.

The logic here is that Io will be focusing on last hits, while using Spirits charges to harass and force back his opponent. Spirits is very strong at Lv 3 and Lv 4, and can inflict 375-500 magic damage with a very short cooldown. Because Io is gaining solo experience at mid, your access to these strong damage spells comes much faster than in normal laning situations. Use Fountains and Bottle w/ runes to maintain your mana and continue harassing the enemy player. Smart plays using Tether to close the distance can earn you early kills.

INTERMEDIATE ITEMS
Armlet of Mordiggian
Armlet provides a wealth of important stats for Io, including +7 HP/sec, +9 damage, +25 attack speed, and +5 armor. When activated, it provides an additional 56 damage, ~450 HP, and +4 armor, but drains 45 HP/sec!

It's important to put this in perspective. If you follow this build and purchase Armlet at, let's say, Lv 11, Io has 81 damage. Armlet activation increases that by almost 70%, to 137. If you are careful with how you use Armlet (i.e. not leaving it on for 2 minutes and running your HP to 1) you have the opportunity to turn your melee damage output from a 4 to a 10 very, very quickly. Please see the section "Why Armlet + Overcharge?" for a more-detailed explanation of how powerful this item can be.

You can activate Armlet in short bursts to last hit more effectively. This will help secure future items in a short period of time.

Armlet can also be activated to temporarily increase your HP by ~450. This can be used when Io has very low HP to provide a temporary buffer that can keep him alive, by de-activating/quickly re-activating Armlet between enemy attacks. Skillful use of Armlet de-/re-activation can save your life by continuously buffering your HP back to ~450, buying you time to finish a kill or escape and heal.

Urn of Shadows
This carry build relies on Io to hurt himself, through Armlet and Overcharge, as well as insert himself in fights as a dominant damage-dealing hero. As a result, Io needs a dedicated healing item that will help to replenish the health lost during fights. Urn of Shadows provides a 400 HP heal over 8 seconds, and can be used secondarily to heal a Tethered ally for 600 HP. The offensive use of Urn is a 150 Pure Damage debuff that can increase Io's DPS and secure kills.

Power Treads
Power Treads increase Io's attack speed +25 and provide +10 of a single stat. Tread-switching is viable on Io to limit mana usage from Spirits casts and to increase health restored from healing items.

ESCAPE/INITIATION OPTIONS
Shadow Blade - 2700 gold
Shadow Blade provides +22 damage and +30 attack speed, which compliment Io's carry role immensely. It also provides an invisibility buff that can be used to escape a bad fight, or to initiate on an unsuspecting enemy hero (causing an additional 175 damage).

Your Spirits are invisible to the enemy player when you are invisible, meaning you can 1) activate Spirits, 2) activate Shadow Blade, 3) approach an enemy hero and run into them, damaging them with Spirits, and 4) break invs by attacking them (activating Armlet + Overcharge) and dealing massive damage in a short period of time.

Shadow Blade can also be upgraded into Silver Edge later in the game, which is useful to Break enemy's passive abilities, especially for heroes like Phantom Assassin, Bristleback, and Anti-Mage.

Hurricane Pike - 4625 gold
Hurricane Pike is a great item for Io because it can be used in a variety of different ways. It can act as a basic Force Staff (with a shorter cooldown), pushing you or a teammate 600 units in a given direction. It can also act as a way to outplay your opponent by Hurricane Piking them away from you. You are still able to attack (as long as you have vision of the opponent) and have unlimited attack range for 5 seconds and a boost of 100 attack speed. If you use the Pike on an enemy, you both move 450 units away from the point of activation (900 units total).

This is very important because of the self-damaging aspect of this build. Io is able to output immense damage but will be running around with 50% HP - in order to keep Io alive and buy time to heal, use Hurricane Pike to escape bad situations and outplay brave opponents.

Not only that, but the increase in stats from Dragon Lance's +12 Str/+12 Agi to +15 Str/+20 Agi/+10 Int supports both Io's mana pool and his attack capabilities. The +6 HP/sec is a nice bonus as well.

Personal Notes - I was using Hurricane Pike for a long time in this build because I found the Force Staff applications to be very helpful, alongside the +6 HP/sec passive healing boost. But, upon comparison with Shadow Blade, S.B provides +22 damage and +30 attack speed for 2700 gold, where as H.P provides +15 damage and +20 attack speed for 4600 gold. Sure, Hurricane Pike provides a range extension for Io's melee attacks, and has a Force Staff capability built into the item, but I have felt more recently that it is important for Io to focus on what makes a carry a carry - damage output - moreso than on the bonuses that Hurricane Pike provides.

Why Armlet + Overcharge?

Armlet drains 45 HP/sec, while Overcharge drains 6% total HP/sec. That's a lot!!! Why self-damage so aggressively? Is it really worth it?

Allow me to introduce - Math. (all formulas taken directly from Dota 2 Wiki)

Io has a BAT (base attack time) of 1.7, meaning he attacks once every 1.7 seconds.
The inverse of this is 1/1.7 = 0.588 attacks per second. This is your base attack speed (represented as the number 100).

The following formula represents the change in attacks per second as increased attack speed (IAS) is gained.
Attacks per second = [(100 + IAS) * 0.01) / BAT]

1 Agility = 1 Attack Speed.
Io has 14 base Agility + 1.6 per level. Therefore, at Lv 17, Io has 14 + 25.6 = 39.6 Natural Agility

Io gains +70 Attack Speed from the following items: +25 Armlet of Mordiggian, +25 Power Treads, and +20 Hurricane Pike.
Io can Overcharge for an additional +70 Attack Speed when Overcharge is max lv.

PRESUMING YOU HAVE Power Treads, Armlet of Mordiggian, AND Hurricane Pike AT LV 17 -

NORMAL ATTACK
(100 + 70 + 39.6) * 0.01 / 1.7 =
2.096/1.7 = 1.233 <-- Io attacks 1.233 times/sec
1/1.233 = 0.811 -> Io has 0.811 seconds between attacks

OVERCHARGE ATTACK
(100 + 70 + 39.6 + 70) * 0.01 / 1.7 =
2.796/1.7 = 1.645 <-- Io attacks 1.645 times/sec
1/1.645 = 0.608 -> Io has 0.608 seconds between attacks

3 attacks at Normal Speed require 0.811*3= 2.433 seconds
4 attacks at Overcharge Speed require 0.608*4= 2.432 seconds.
4/3 = 1.33 <-- That's a 33% increase in "attack speed" when you Overcharge!!!

ARMLET MATH
Normal attack damage with items Urn/Armlet/Treads/Pike at Lv 17 is 116 damage.
Armlet attack damage with items Urn/Armlet/Treads/Pike at Lv 17 is 172 damage. (+56)
172/116 = 1.483 <-- Armlet activation increases my outgoing damage by 48.3%

3 attacks of 116 = 348 damage
4 attacks of 172 = 688 damage
688/348 = 197.7%!!!

You are effectively DOUBLING YOUR DAMAGE OUTPUT by Armlet + Overcharge co-activation.


Let's study this same idea earlier in the game, when Io is Lv 11, and has only Armlet of Mordiggian, Boots of Speed, Urn of Shadows, and Bottle. No fancy damage or attack speed items yet.

Io gains +25 Attack speed from Armlet of Mordiggian.
At Lv 11, Io has 14 + 16 = 30 Natural Agility.

NORMAL ATTACK
(100 + 25 + 30) * 0.01 / 1.7 =
1.55/1.7 = 0.912 <-- Io attacks 0.912 times/sec
1/0.912 = 1.096 -> Io has 1.096 seconds between attacks

OVERCHARGE ATTACK
(100 + 25 + 30 + 70) * 0.01 / 1.7 =
2.25/1.7 = 1.324 <-- Io attacks 1.324 times/sec
1/1.324 = 0.755 -> Io has 0.755 seconds between attacks

11 attacks at Normal Speed require 1.096*11= 12.056 seconds
16 attacks at Overcharge Speed require 0.755*16= 12.08 seconds
16/11 = 1.45 <-- That's a 45.45% increase in "attack speed" when you Overcharge!!!

ARMLET MATH
Normal attack damage with items Urn/Armlet at Lv 11 is 81 damage.
Armlet attack damage with items Urn/Armlet at Lv 11 is 137 damage. (+56)
137/81 = 1.691 <-- Armlet activation increases my outgoing damage by 69.1%

11 attacks of 81 = 891 damage
16 attacks of 137 = 2192 damage
2192/891 = 246.02%!!!

When you co-activate Armlet + Overcharge at Lv 11, you are increasing your damage output by almost 250%!!! The earlier you use Armlet + Overcharge in the game, the bigger their effect will be.

Items (Late Game)

End-game carry items will be match-specific, so you must decide which are the best items to defeat your particular set of opponents.

Desolator (3500 gold, +50 damage)
Desolator allows Io attack high armor heroes and push more effectively. Deso reduces the armor of any right-click target by 7 for 15 seconds, allowing the rest of your team to increase their physical damage output on that target. This works especially well on structures like Towers or Rax. Deso combos very well with Daedalus to perform uber-critical attacks.

If you purchase Desolator, DO NOT GET Satanic or any other lifesteal item. Both lifesteal + armor reduction are unique attack modifiers and do not stack.

Heaven's Halberd (3400 gold, +45 damage and +400 HP)
Heaven's Halberd is a great item for Io. The damage-to-cost ratio is very favorable, and it also buffs Io's HP to help keep him alive. The Disarm function of Halberd effects melee heroes for 3 seconds and ranged heroes for 5.5 seconds. The best part of using Halberd's Disarm is that it will take 1-2 seconds for the enemy player to realize he can no longer attack, and in the meantime, his hero is standing still as you and your team attack. Great for ranged carry and DPS ( Huskar, Clinkz, Drow Ranger) and melee carry, too ( Ursa, Wraith King, Sven).

The Lesser Maim proc is somewhat ineffective for ranged heroes - a 35% chance to slow attack speed by 10 and move speed by 10% for 5 seconds. -10 attack speed is not even noticeable, whereas -10% move speed might help, but shouldn't be relied on. This is more of an incidental bonus than a game-winning strategy.

Black King Bar (3975 gold, +34 damage and +200 HP)
BKB is a more defensive, safer choice against crowd control and high-damage spells. If Io is struggling against magic-based heroes in the mid/late game, this is a great choice to ensure Io survives the teamfight.

BKB works very well in combination with Satanic, by ensuring you are not interrupted from attacking during the Unholy Rage 200% lifesteal buff.

Monkey King Bar (5200 gold, +66 damage and +56 magic damage)
If your enemy team is building evasion items, speccing evasion talents, or building Radiance (or you're up against a Phantom Assassin), MKB is a great choice for ensuring every Io attack finds its mark. MKB provides +66 damage and a 35% chance to mini-bash, which deals an additional 160 magic damage and a 0.1 second stun. This averages to an additional 56 magic damage per attack (160*.35 = 56), meaning this item hits far harder than its +66 label implies.

Completing the item is an easy extension from Demon Edge.

Daedalus (5325 gold, +76 damage and +40.5% total attack damage)
Daedalus provides you a 30% chance to crit for 235% of your normal attack. This averages to a 40.5% increase in your attack damage (135*.3 = 40.5). Daedalus works very well with Desolator to output massive-damage crits.

Completing the item is an easy extension from Demon Edge. However, Crystalys actually provides more damage than Demon Edge (when averaged across its crit chance).

Satanic (5700 gold, +75 damage and +500 HP)
Satanic fattens Io up, provides 25% lifesteal (which is a lot for a ranged hero), and can be activated to provide a total of 200% lifesteal for 4.5 seconds. Because Io is damaging himself through Armlet + Overcharge, a lifesteal item of this power can have a big effect on Io's sustainability within teamfights. Ensure to activate Satanic when there are no disables available to inhibit your ability to attack. If you can buy Crystalys or Daedalus, critical strikes will heal for huge amounts of HP.

If you purchase Satanic, DO NOT GET Desolator. Both lifesteal + armor reduction are unique attack modifiers and do not stack.



There are several experimental items that are untested, but theoretically could make strong end-game items.

Diffusal Blade (3150 gold, +40 damage, +25 attack speed, +3.5 armor, +120 MP)
I'm not gonna lie, the more and more I read about Diffusal Blade, the more I want to buy this item immediately after Hurricane Pike. The ridiculously cheap cost of 3150 gold makes it an easy item to purchase. The +25 Agi and +10 Int support Io's armor, attack speed, and mana pool. Not only that, but Diffusal Blade deals +40 damage per hit through Mana Burn, which burns 50 mana per attack (80% of which is dealt as damage). You can lifesteal from this damage, but it will not add towards a crit.

You gain the ability to Relocate with a teammate onto a single enemy hero, Purge/Slow that enemy for 4 seconds while you wail on them with melee attacks, and escape before help can arrive. You can Hurricane Pike an enemy hero, Slow them as they charge back at you, and ruin them with melee attacks (and a bonus 100 attack speed from Pike). Not to mention the natural synergy between Mana Drain and increased attack speed from Overcharge - you'll be shredding enemy's mana in no time flat. And once your charges are finished, spend another 700 gold to strengthen the item (+35 Agi, +15 Int) and replenish its charges.

Great against mana-reliant carries like Wraith King and Medusa, great against strong buff heroes like Omniknight (dispels Guardian Angel, not Repel), Legion Commander, and Monkey King (dispels JINGU MASTERY BUFF!), and great against activated items like Ghost Scepter, Urn of Shadows, and Eul's Scepter of Divinity. It can even dispel every single Rune buff (excluding Invisibility).

Orchid Malevolence (4075 gold, +30 damage, +30 attack speed, +300 MP, lots of MP regen)
Orchid provides a 5 second silence. Once the silence ends, the enemy hero takes 30% of all damage dealt to him during the 5 seconds. Great for shutting down escape heroes like Weaver and Anti-Mage. Orchid can be extended into Bloodthorne in the late-late game.

How to Use Tether/Spirits/Overcharge/Relocate

I have written extensively about how you can use Tether, Spirits, Overcharge, and Relocate in my general Io guide.

Rather than doing lots of copy + pasting, I'll just provide a link instead: https://www.dotafire.com/dota-2/guide/the-1500-commend-io-guide-7-06-and-above-26120#chapter7

Mid Heroes - Who is Gonna Kick Your Ass?

EZ PZ TIER
Invoker
Invoker is focused on getting his Midas, and thinks you are weak and easy. What a fool. In reality, you can out-DPS Invoker's melee attacks using Spirits and can Tether away from his Cold Snap combo. He will need to spend time regening HP with his Quas orbs, reducing his melee damage and allowing you to control last hits. Invoker gets stronger as the game progress, but in the early game, his last-hit focused mindset makes him easy.

Pudge
Pudge is a great opponent for Io. You can box him out of last hits using Spirits and melee attacks. You should only be scared of his Hook. A simple Observer Ward will negate his Hook chances if you are truly nervous, and if you are Hooked, you can always Tether back to your own creeps to regain strong positioning. Also long as you use smart positioning by standing behind creeps, you should stay alive fairly easily and dominate the lane.

Puck
Puck, despite his recent melee attack buffs (+6 damage patches 7.03/7.04), plays a lot like an Invoker would. He is keen on last-hitting to rush out a Blink Dagger/Veil of Discord, and his spells are weaker than Io's until he can develop a 2nd damage spell at Lv 8 and above. His Phase Shift ability renders him immobile, which gives Io time to approach with Spirits and deal massive damage. As long as you are careful to watch for initiation through Illusory Orb, Puck should be no problem for Io.

Magnus
Like Pudge, you are able to box Magnus out of mid-lane control through your Spirits spell. His reliance on melee damage makes him a poor lineup against Io. Be careful for ganks, because his Reverse Polarity is a good set-up to get you murdered by a 2nd hero. As long as you don't position yourself between him and his tower (so that he can Skewer you out of position), you should not struggle in this lane.

Sniper
Sniper is able to control last hits slightly better than Io because of his rapid missile speed, but his low opening damage, lack of escape, and weak HP make him a viable target for Io Spirits. His melee range might make him difficult to kill on your own, but a Relocate gank behind him (between him and his tower) will earn you easy kills.

COMPLEX TIER
Shadow Fiend
Shadow Fiend is a complex hero to fight against because of his ability to explode in effectiveness if not controlled. You are actually able to out-last hit an SF at Lv 1, and can use that to your advantage to slow his Necromastery gain. His weak HP makes him EXTREMELY vulnerable to Spirits damage. However, if you die to SF before you can kill him, the lane is borderline lost. His explosive melee damage and Razes will control last hits and force you out of lane, making life very difficult for you.

Zeus
Zeus is dangerous because he can match your magic damage output and your range. He is able to very quickly knock down Io's HP, especially after Lv 6 when he has his ultimate. However, Io has a position advantage because you can initiate via Tether, and Zeus has low HP that renders him weak against Spirits. This lane requires careful positioning to not get caught with low HP and quickly zapped to death. Purchase a Magic Stick ASAP.

Queen of Pain
QOP has a minor advantage over Io, because she can change her position quickly and burst you down with magic damage. She will control runes better than you, and if you let your HP get too low, QOP will blast you back to the stone age. That being said, you can last hit effectively against QOP, she is weak against Spirits, and if you are able to maintain your HP, laning against her should be no problem.

Storm Spirit
Storm Spirit works similarly to QOP, in that after Lv 6 he can rush your position and deal large amounts of damage. You should be able to control the lane before Lv 6 due to his poor melee range, but once he has his ultimate, your ability to control will drop rapidly. A strong lane from Lvs 1-5 is important to survive and thrive once you both hit Lv 6.

Viper
Viper, like you, is a bit of glass cannon. His Poison Attack debuff slows and damages you, while his passive damages you again, even when you use Spirits. But Viper has low HP, and is very item-reliant to stay alive (hence why many Vipers rush either Mek or Shadow Blade). Once again, positioning is key - if Viper can catch you and chain his Poison Touch or use his ultimate, it will be difficult for you to survive. If you can keep him at 50% HP with your Spirits, however, his aggression will fade very fast.

Outworld Devourer
OD hits like a tank, and steals your Int in the process. That being said, his normal early-game strategy is to level up Astral Imprisonment first, and the range on this spell is very poor. It will be very obvious when OD wants to attack you, because he'll be running right at you every time. Use Spirits to force him back and out of the lane for some level of creep control, although it will be difficult to farm against this hero.

Tinker
Tinker is an interesting opponent because his early game varies depending on his talent selection. I think most Tinkers would see an Io across the river and think "Laser + Rockets, lets blow that kid up", and that might begin to cause problems for you after Lv 6. However, Io is will absolutely be able to control last hitting is Tinker specs this way. If Tinker specs heavily into March of Machines, he gains creep control but loses the ability to kill you. Smart positioning and understanding how visible you are is key to winning this lane matchup.

************ TIER
Templar Assassin
TA is probably the worst possible opponent for an Io. Her Refraction ability absorbs your Spirits charges while increasing the damage you will feel from her Psi Blades passive. She is able to harass you through creeps, while blocking your major damage source through her shield. An Urn of Shadows charge is able to quickly eat through her Refraction defense, but even then, her immense damage output through Meld and other skills makes her incredibly difficult for you.

Ember Spirit
Ember Spirit is difficult because his Flame Guard ability absorbs the full 500 magic damage from your Spirits. This means you must hit all 5 orbs (at lv 7) to knock out his shield, during which he will be charging at you with melee attacks and Searing Chains ready (not to mention the potential for a triple-cast Fire Remnant). While you might be able to get last hits in the this lane, you will have a very hard time killing Ember without a gank from your teammates, and his ability to control the lane will increase as the game progresses.

Talents

In this section I defend my logic behind my Talent choices.

Lv 10 --> +6 Armor or +10% Magic Resistance
Normally, I would say this talent selection depends upon what enemies you're facing - a dominant magic-damage team would require additional magic resistance, while a melee-focused team would require more armor. But I think a deeper understanding of what "+6 Armor" and "+10% Magic Resistance" actually offer is required to compare the two talents.

The +10% Magic Resistance talent buff is low compared to other items you can purchase (such as +15% from Cloak), and is calculated AGAINST the 25% natural magic resistance all heroes have, in the following formula 1-((1-0.25)*(1-0.10)) = 32.5%, meaning the +10 Magic Resistance talent only nets you +7.5% magic resistance!!!

In comparison, Io at Lv 9 has 1.83 natural armor, which blocks 10% of incoming physical damage. At Lv 10, Io has 2.06 natural armor plus 6 armor from the talent, producing 32.5% physical damage block, and increase of +22.5%!!! Once Io gains the 5 armor bonus from Armlet of Mordiggian, this rises to 44% physical damage block at Io Lv 10 (51% blocked with Armlet activated).

If Io instead chose the +10% Magic Resistance talent and acquired Armlet at Lv 10, he would block 30% physical damage. This means that the difference between {Armlet} and {Armlet + Lv 10 Armor Talent} is approximately 14% physical damage block.

So...in summary...
(1) If you have no Armlet at Lv 10, +6 Armor talent gives you +22.5% physical resistance (32.5% total)
(2) If you DO have Armlet at Lv 10, +6 Armor talent gives you +14% physical resistance (44% total)
(3) If you DO have Armlet at Lv 10, +10% Magic Resistance talent gives you +7.5% magic resistance (32.5% total) and leaves you with 30% physical resistance.

My personal instinct would be to choose the +6 Armor Talent because of the high physical damage block (with or without Armlet) as compared to the measly +7.5% magic resistance of the +10% Magic Resistance talent.

Math Proofs
Io Agility 14 + 1.6 per level --> 14 + 12.8 = 26.8 * (1/7) + -2 base armor = 1.829
1 - 0.06 * 1.829 / (1 + 0.06 * 1.829) = 90.11% <-- blocks 10% physical damage
Io Agility 14 + 1.6 per level --> 14 + 14.4 = 28.4 * (1/7) + -2 = 2.057
1 - 0.06 * 2.057 / (1 + 0.06 * 2.057) = 89.01% <-- blocks 11% physical damage
1 - 0.06 * 8.057 / (1 + 0.06 * 8.057) = 67.41 <--- blocks 32.5% physical damage
1 - 0.06 * 13.057 / (1 + 0.06 * 13.057) = 56.07 <-- blocks 44% of physical damage

Lv 15 --> +10 Mana Regen or +10 Strength
+10 Mana Regen. It's not even a competition. It's not even a f*cking question. This is the most blatant choice of all the talents Io has, and let me explain why.

+10 Mana Regen is insane. That Talent will fix your mana regen for the entire game. NO FURTHER MANA REGEN ITEMS REQUIRED. This is single-handedly the biggest buff to Io in the 7.00 Patch. Overcharge without fear of losing all your mana. Spam Spirits to your heart's content. I really cannot overstate how insanely important this talent is.

Another way to view this is through cost. How much gold would it cost to buy items that would offer you the same effect as the talent? Well, +10 Strength is a Ogre Club, which is 1000 gold. +10 Mana Regen....is not even fathomable. A Eul's Scepter that cost almost 3000 gold would not provide +10 Mana Regen.

This allows Io to reserve Bottle charges for mainly HP restoration, rather than MP maintenance. Spirits is still a very powerful at this point in the game (especially so because Io, being solo mid, will hit Lv 15 before the majority of enemy players), and the +10 MP Regen talent allows Io to constantly have a set of spinning orbs available to smash into opponents.

Pick this talent. Anyone who says otherwise is a fool.

Lv 20 --> +20 HP Regen or +120 Gold/min
The gold gathered from the +120 GPM talent allows you secure important end-game carry items. This is crucial, because the effectiveness of Io begins to transition from { Spirits + right-clicking} to mainly {just right-clicking} between Lvs 15 through 20. After Lv 20, the 500 magic damage from Spirits is becoming less and less effective, and it's important to purchase expensive, high-damage items to keep Io as a functional carry. Items such as Daedalus, Monkey King Bar, and Satanic are over 5000 gold each, and this talent will help secure the gold required to complete those items and defeat strong enemy heroes.

The +120 GPM talent helps supplement Io's gold intake and allows him to transition into the endgame far better and with more versatility than the +20 HP regen talent.

Lv 25 --> +150 Spirits Damage or -50 Seconds Respawn
The +150 Spirits Damage is an incredibly strong boost to your Spirits spell, which by Lv 25 has become less-than-lethal and more like mildly-annoying for the enemy. If you are skilled with the movement of Io's Spirits, this talent is a DEADLY choice. The damage of a full Spirits cast moves from 500 magic damage (5 orbs x 100 damage) to 1250 magic damage (5 orbs x 250 damage), which can be effectively stacked to 2500 Magic Damage.

Let me repeat that. 2500 Magic Damage. This completely revitalizes the Spirits spell and truly makes it a deadly end-game weapon (especially when combined with debuffs that increase magic damage such as Veil of Discord or Ethereal Blade).

That being said, -50 Sec Respawn Talent has its uses. -50 sec respawn would provide you a quick respawn to get back out into the field and continue defending/farming/pushing if you're killed. This might make sense, because the majority of Io's damage has been focused into his right-clicking, so adding more damage to his spells might just be unnecessary at this point. I can imagine a situation whereby the -50 Sec Respawn could be useful after a team-wipe, for Io to be waiting at his Rax ready to defend a big push by the enemy.

I realize this is a counter-intuitive view of the Lv 25 talent ("-50 Sec should be for SUPPORTS and +150 Spirits should be for CARRIES"), and I must admit, I have never tested the -50 Sec Respawn on a Carry Io, but I definitely see the validity of its selection for a carry player.

Outro

I will be updating this guide as I practice more and more with Io Carry. I probably play one Mid-Lane Io game for every 25 Support-Lane Io games, so while I do have experience, I definitely have room to research and improve. I have listed some powerful but unorthodox items and item combinations, and I will be adding/removing items/combos as I experiment in the future.

Check back on this guide in a month to see what's been updated!

If anyone has any questions/suggestions/comments on the build, let me know by leaving a Comment below! I'd be happy to talk Io-shop any day :-) (as long as you don't mind long, rambling responses)

- Wisper