"What is a... Mana?" The Volcanic Glass Destroyer

Come and Listen, Human. For I have Knowledge to Share...

I have heard tales and lost legends that many magi in this plane suddenly lose the ability to cast their spells. They say that in the time they have utilized these spells they have exhausted their reserves of... "Mana." I know not such a concept, as I nor any of my allies have ever experienced this "Loss of Mana." All I know is the infinite arcane torrents that surround me, ever grow as I fight, becoming vast enough to lay waste to my foes before me with but a single point of my scepter.

I am the Obsidian Destroyer.

Introduction

Alright, lets go ahead and get it out of the way:
1. Do not talk about Outworld Destroyer
2. DO NOT talk about Outworld Destroyer
3. This is a very hard build to pull off, but will reward your team infinitely if you do.
4. Outworld Destroyer (Obsidian Destroyer in Dota1) is NOT a carry you should be expecting to play in every single game.
5. Yes, I do some very Taboo things with this build. Outworld Destroyer is not your typical carry, and will require you to do some very odd things in order to play him to his fullest extent.

Now that we have clarified some things let me get to explaining WHEN you should pick OD.

When or when NOT to pick the Black Sphynx.

WHEN to pick Outworld Destroyer:

No one has declared Mid
(Outworld Destroyer goes MID! No Exceptions)

When the enemy team has a majority of Strength and/or Agility on their team.
(OD wrecks all non-Int's lategame. Few Exceptions)

When the enemy team has a non-Int Mid you would like to counter, such as Pudge.
(OD is very effective against physical damage due to his naturally high Agility/Armor. Exceptions)

When the enemy team has a Phantom Lancer and/or Chaos Knight you wish to grind into paste.
(OD will tear a structurally superfluous new behind in any and all illusions. No Exceptions)

Your team is very "Mana" hungry... Whatever that means.
(OD at level 7 is a better mana dispenser than Gandalf and Wisp with Arcane boots combined. No Exceptions)

When NOT to pick Outworld Destroyer:

That Structurally superfluous behind of a pug auto-locked a Mid Champ.
(Outworld Destroyer IS the Mid lane. Don't even solo top/bot with him. 1v1 is where he needs to be)

Your team lacks any kind of AOE Hard CC
(If you don't have a Sven, Tiny, Rubick, or Similar Hero as an ally, chances are you'd fail without one. If this is the case, for the love of Zeus, please help your team and play a disabler instead of a Carry.)

If the Enemy team has 4 or 5 Intelligence heros.
(If this is the case, OD isn't going to be doing **** to anybody in teamfights, play a hard INT counter instead, Like Nyx Assassin.)

If the Enemy team has a lot of Silences, or a Silencer.
(OD becomes glass -pun intended- without the cannon if he becomes Silenced for any real period of time. You MAY be able to counter with a BKB, but that'll take ALOT out of your carrying power)

If you'd like to cast spells and be doing something before Level 8.
(Sorry Jingle Bon Hovenwitts, but try out a different Ranged Solo Mid INT hard carry... If there is one. OD has quite possibly the most BORING early game, being solely committed to last-hitting and denying creeps until he can sustain his ORB effect indefinitely. Until you max out your Aura, you shouldn't have to cast a spell.)

Items

Since I'm the Pessimistic -Glass half full of cat urine- kinda guy, lets start off with what you DON'T buy EVER:

Arcane Boots:
While you do get additional true damage on your Arcane Orb from the mana that these boots give you, It doesn't total up to the DPS that you can get with the attack speed the Power Treads give you. I've done the math, trust me... I'm a Doctor.

Aghanim's Scepter:
Outworld Destroyer has the WORST scepter upgrade out of any character in DOTA. All it does is increase the damage you do with your ult by 1 damage per point of INT they have less than you. End-END-Game this averages a WHOPPING 40 damage past resistances, Woohoo. 4200 gold wasted for 40 damage to your ult.
You can spend as much gold getting a rod of Atos and a quaterstaff, Tripling the damage you get from the Scepter's stats while only sacrificing ~100hp.

Morbid Mask, Maelstrom, Ghost scepter:
These should be obvious, they all prevent you from using your bread-and-butter ORB True Damage orb effect.

Chrysalis:
Even though OD IS a carry, you don't want to be focusing on his physical damage, You want to be able to break through all those defenses the Strength Tanks and High-agility carries. Get Mana and INT, not Pure Damage and Crit. The First two sources of damage will stack with Damage increase auras, the last two won't.

Divine Rapier:
You're just asking for trouble now, son.