Naming the monsters.

[Mekose]

Well, the official names in the files are Grunt, Brute, and Water Lurker.
The Water Lurker is also referred to as the Water Horror and it's actual name the Kaernk.
The Grunt is

Spoiler below!

sacrificed or experimented on servants by Alexander, there are a lot more than one. Alexander mentions in a note that he needs to "create more servants"

I have no idea what the Brute is. There is one flashback that mentions a man being tortured calling Alexander a brute. I believe this man to be the captain of the guards sent to investigate Brennenburg.

Spoiler below!

Before the cellar you read a note talking about a platoon of guards to investigate Brennenburg castle. Alexander locks them in the cellar.
In the cellar in the room with all the gore, a flashback is heard of a man raving about what happened.
Later the same man is heard screaming at Alexander while he is being tortured and mentions the word "brute".
When you inject yourself with the dead mans blood in the morgue.
There is a room with a ton of bones, bloody scratches on the walls, and ripped out plants of wood.
When you enter this room the same man is heard screaming "Let me out, someone help me!".
Seeing as the Brute is wearing armor and has a sword. It would make sense that since the captain survive, Alexander decided to experiment on him creating the Brute.

For fun my friend and I renamed everything. We named the Grunt "Mr Sacky", The Brute "Tinny", and The fleshy stuff "Grace".