The Changeling is one of the 10 races avaliable for play. It can be unlocked by killing special enemies, which sometimes will drop throphies. If playing with the Adventurer class, the throphy will have a 100% chance of unlocking any class & race, which may be the Changeling or any other race not already unlocked. If playing with another class than the Adventurer, the throphy will have a 50% chance of levelling that class up, and a 50% chance of unlocking a new class & race.
Unlocking the Changeling also unlocks the class: Mage
Racial bonus: Shapeshift (Killing a Special skull refills the cooldown of one of your skills, possibly an already full one)
Mortal enemy: Unstable (Replaces all the tiles with new ones when the countdown runs out. When playing with other races, the new tiles will not contain any skulls)
Mortal enemy effect: The new tiles will contain skulls, and no swords