Soulfire Zeal

Soulfire Zeal is an Exotic Trait and the catalyst for Cull's Shadow. While the weapon is equipped, nearby soulfire crystal detonations increase damage resistance and movement speed. To unlock it, equip Cull's Shadow behind the Oblation: Soulfed arena, look at the six Hive rune discs on the statues, and shoot them from top to bottom in the order shown on the weapon. Shooting the discs opens the final mission, Immolation, and grants the catalyst.