Brain in Jar Character from the first trailer Spoiler possibly.

[Kein]

There's a monster/character name Aker who's motivations are insanity and odd religious ferver[...]

As I understood it, every monster in the game is an existing crew member or brain scan. The game explicitly tells us only about Aker and his 3 Proxies, but the first (Worker), second (Catherine calls him "Brute") and the rest monsters didn't appear out of thin air. It just takes some thinking to connect the dots. I'm lazy.