Archdeacon McDonnell

Archdeacon McDonnell is a minor posthumous antagonist in Dark Souls III. Once a leading member of the Church of the Deep, he is the leader of the Aldrich Faithful covenant, a group of rogue warriors dedicated in guarding their god, Aldrich.

Biography
McDonnell was one of the three archdeacons from the Church of the Deep alongside Royce and Klimt. Alongside Pontiff Sulyvahn, they worshiped Aldrich through his grave, offering sacrifices to please his cannibalistic ways. To McDonnell, the souls that stagnated around the cathedral delighted him, as he viewed them as the world's bedrock. McDonnell also had a hobby of collecting "dregs", substances that contain the power of the Deep that exist in all lifeforms. With dark sorcery, McDonnell shared his dregs among the deacons to make them become both clergymen and sorcerers.

When Aldrich was revived as a Lord of Cinder, McDonnell chose to accompany Aldrich and Sulyvhan in their plan of overthrowing Anor Londo, casting off his white crown and gave his Deep Soul spell to Royce. Prior to the games events, in Irithyl of the Boreal Valley, McDonnell practiced channeling faith into his sorcery, which was seen as a trespass to his religion. In either hiding or imprisonment for his taboo act, he passed away within the hidden Water Reserve room.

McDonnell's corpse can be found at the left end of the hidden Water Reserve room found in the left wall of the building beyond Sulyvahn's arena and the courtyard with the dead giants. Defeat the two Sulyvahn's Beasts guarding the room first before interacting with McDonnell. Despite being dead, he still holds enough power to grant people access to the Aldrich Faithful covenant. The item used by the covenant are Human Dregs that McDonnell admires: granting 10 gives the Great Deep Soul spell, and giving 30 gives the Archdeacon Great Staff.

Trivia

 * It is unclear how McDonnell died, either he was killed by the Sulyvahn's Beasts, or from the black goo under his eyes, he may have been exposed to the Deep itself.
 * McDonnell may be derived from the Gaelic name Domhnall, meaning "ruler of the world".