Kirk, Knight of Thorns is a black phantom NPC that invades three times throughout the game at different instances. By killing him all three times, one is able to obtain his armor, the Set of Thorns. He will invade your game at all of the three places, regardless of whether you defeated or were invaded by him previously. Kirk is a Chaos Servant, presumably invading to collect humanity for The Fair Lady.
You will find him after defeating the Ceaseless Discharge. Make your way to the now cooled lava ground, continue to the next area. You will go down some stairs on the side of a cliff and as you do this he will invade. Note that he only spawns after you put the Lordvessel on the Firelink Altar (the orange light barrier already gone allowing you to fight Demon Firesage).
- Black Phantoms will only spawn if the player is in human form and the area boss has not been defeated. This means that defeating a boss before being invaded by a particular NPC Black Phantom will forever deny that Black Phantom from appearing in that area on the current playthrough.
- Unlike other Black Phantoms, his weapons do not have 100% drop rate.
- If Kirk falls off a ledge, once the loot appears, just quit and reload your game and the loot will be where Kirk was last standing before falling off.
- Once defeated, his corpse (containing Set of Thorns) can be found in the back of the Daughter of Chaos bonfire chamber in Quelaag's Domain.