Reyhiem

Reyhiem (レイヒム), an archbishop of the Western Holy Church, was the most powerful religious figure in the Kingdom of Falmuth. He was (on paper, at least) on an equal position of power as the king himself given Falmuth's adoption of Luminism as its state religion. That was just a formality, however; in reality, Reyhiem was more of a trusted right-hand man, taking his cues from the king.

Personality
Reyhiem is an opportunistic coward who always curries favor with authoritative individuals, even going as far as to talk about Monster extermination being a matter of course one moment, then offering himself as a lobbyist for the interests of Tempest's Monsters right after. However he is also earnest in fulfilling his current role as long as he isn't inclined to change his allegiance.

Story
Reyhiem helped King Edmaris on his invasion against the Jura Tempest Federation by providing Temple Knights alongside setting up a Prison Field, a barrier that weakens monsters within the barrier, around Rimuru City.

He was captured by Rimuru alongside King Edmaris and Razen and was interrogated and tortured for weeks in Tempest.

He then pledged loyalty to Diablo in exchange for his life and was sent to give a message to Hinata Sakaguchi from Rimuru.

Unfortunately for him, he was killed by The Clerics of the Seven Luminaries who were aiming to alter Rimuru's message to incite further conflict.