Gabriel

Supposedly from the Thalum Mercenary Company, sent as an envoy of the Emperor (Damian von Beryth IV). Gabriel causes a bug to bite Nim, causing her to periodically glow purple, as is later revealed to be when Gabriel is tracking Nim. While exploring Thetis’s underwater temple, he appears as the party is fighting the water elemental, turning the water elemental against us. He threatens us with death in return for the Sapphire, also talking about preventing witnesses.

He is not humanoid (Hold Person does not work on him).

He appears to be allied with Nyarlathotep, hence why he was trying to stop the party from reviving Thetis. Thetis says Gabriel is a lot more dangerous than you think.