Obliteration is a weapon used in the Crucible. It is obtained from killing a Supreme Champion or being the champion yourself. This is the magic version of the three Supreme weapons, the ranged version being Decimation and Annihiliation for melee. Clicking the "Devour" option will collect trophy bones from those you have killed. It also has a special attack that hits surrounding players with magic.
Obliteration, along with Annihilation and Decimation, is dropped by Ded Meet when killed during the tutorial, The Supreme Champion. Although the player is instructed to pick up the three weapons, they could not and the tutorial ends without a chance to use them.