Deathbringer's Will (heroic)

Source
This trinket drops from Deathbringer Saurfang in Icecrown Citadel on 25-player Heroic mode.

While the trinket is very useful for physical DPS classes, it does have its flaws. As its proc causes the wearer to "transform" into one of the races of Northrend, certain actions (such as mounting) are prohibited as a result.

Effects
The transformations the trinket provides are random, last 30 seconds each, and vary between classes.