Migra by glavidus

This is my idea built around passive stealing. Unlike Rubick, whose ability stealing properties are suited for a mage, Migra is an assassin that with proper equipment can turn into a floor clearing powerhouse.
An additional property of his is gaining damage with number of buffs and debuffs the enemy has. This is also manifested in his talents, each of which haunts his enemies with auras, all of them working on separate debuffs. I also got creative with these auras and included some elements that we haven't seen in Dota before.

Q: SINGHOUL - inspired by the Bladetome of Fire Emblem Heroes, this spell's damage output increases with both buffs and debuffs presented on the enemy's status bar. This includes time based status, condition based status, and auras. However, things like Templar Assassin's trap counter, or charge based spells indicators obviously wouldn't count to Singhoul's damages. I don't know if there are flags in the game's engine for this kind of thing, but in any case we could just add exceptions.

All other spells of this hero have debuffs on them, synergizing with Singhoul.
Singhoul will only apply stacks from one enemy. This means that, if Singhoul hits two enemies, one with 5 debuffs, the other with 7 debuffs, Migra will gain 70 damage.

W: HEARTBREAKER - A slow with an added gimmick that counters certain tanky heroes and items. As the skill on it's own doesn't deal "damage" (it has a HP removal flag), it doesn't disable Heart of Tarrasque or Spirit Vessel heal.

E: UNSEAL WRAPS - this skill lets Migra take advantage of the damage he gains from Singhoul. Paired with a mobile cloud of silence, all of this comes at a cost of being more vulnerable to physical attackers. Migra also cannot use items during this spell, serving as a mute counterpart to Mask of Madness. Aside from his ultimate's "defensive" function, Migra has no means of escaping, making timing the use of this spell extremely important.

R: COLLAPSE - the crown jewel of this design, Collapse effectively makes Migra risk his life for huge rewards - similar to Phoenix's sun.
The idea of gaining other heroes' passive skills carries some huge implications, as he can steal ultimate passives as well.
Two major ones most of you probably are thinking of are Marksmanship (Drow Ranger) and Coup de Grace (Phantom Assassin). Being a right clicking agility hero, Migra can benefit heavily from additional DPS. Marksmanship is disabled at a meele range, so it's not so useful for teamfighting, however Migra would still gain the agility when pushing. In other words, after a won teamfight Migra with his team can press objectives more heavily.

This is a major point when thinking of balancing this concept: can this hero be punished? Can his enemies stop him from abusing this power? In total Migra has a silence, slow, decent burst, and a DPS booster. On paper, this sounds broken, however he can't make use of half of it without putting himself in a dangerous spot. And the fun comes from abusing the passive abilities he gains. Thanks for reading.

Other passives worth mentioning:
* Dispersion and Desolate
* Divided We Stand (not sure if that wouldn't have to be disabled actually!)
* Fervor
* Fury Swipes
* Broodmother's Bite
* Greater Cleave
* Flesh Heap
* Athropy Aura
* Greevil's Greed
* all Bash skills (Faceless Void, Slardar, Spirit Breaker)
* Feast
* Berserker's Blood
* Inner Beast
* Jingu Mastery

STR: 20 +2 - engaging as this hero is supposed to be risky. Coupled with self armor loss, this shouldn't be kept high.
AGI: 25 +1.4 - base agility is rather high, however he shouldn't gain a lot of it, seeing as he has two DPS boosters and access to other heroes' passive skills and bonuses from being an agility hero
INT: 18 +2.8 - he casts a lot of spells and his limitations aren't bound to mana, I believe his intelligence growth should be good.