Notes from author
A knight wearing the Black Iron Set, Black Iron Greatshield, and wielding a Greatsword. You first encounter him at the top of a tower in Sen's Fortress as a summonable NPC for the Iron Golem boss fight.
Tarkus is a knight of the lands of Berenike. Knights of Berenike were praised for being near giant in stature, amazingly strong and resilient; Knight Tarkus having strength that surpassed nearly all of his countrymen. It is heavily implied that Tarkus is one of the only undead to complete Sen's Fortress and the area is strewed with Hollowed Baldur and Berenike warriors who were unsuccessful in advancing further.
You encounter Tarkus' corpse in Anor Londo, below and to the left of the Painted World canvas, along with his armor. The placement of the corpse suggests that Tarkus entered Anor Londo and found no other way to progress besides the scaffolding with the painted guardians. His namesake Iron armor leaving him unbalanced on the beams and causing him to fall to his death.
