Enemy of my Enemy
Ultra rare0.5%ObjectiveOptionalSingle-player
Helped the Elite General charge the hill in Osiris on Heroic difficulty.
In Osiris there's a friendly Elite General who pushes up a hill - keep him alive and support his charge, on Heroic. Clear the Covenant and Prometheans ahead of him and don't let him get swarmed. Stick close and shoot anything targeting him, and he'll make it up.