In Dark Souls, whenever you find set items on a corpse, they can be sometimes linked to other NPCs in the game.
Some examples for this are
- Black Iron Tarkus: After you summon him to fight the Iron Golem, along the path into Anor Londo, you find a shattered window, revealing a path along the rafters of a large building. Again, later you find an entrance to the ground floor of the same building, and in the back corner, a corpse, with the Black Iron Set.
- Lautrec of Carim: If you follow his storyline, you end up invading him before your fight with Ornstein & Smough; which you can then find a corpse carrying the Set of Favour. Again, presumably this corpse is meant to be Lautrec.
- (Unnamed) Sealer: you can find the Crimson set in Blighttown, and if you follow the lore, this set apparently belonged to one of the four Sealers that flooded New Londo to seal the Darkwraiths away. This Healer ventured down through Blighttown, and eventually succumbed to the poison, and died.
- Laurentius of the Great Swamp: Once you complete his storyline, you can find him down in Blighttown, hollowed. Again, you can find a corpse near the location where he attacked you, carrying the Pyromancer Set.
So is there any clue as to who the owner of the Elite Knight Armour set is?