Transfusion is a port of the game Blood to the DarkPlaces Quake engine.
Currently not all levels are ported, and only multiplayer is supported.

From the original game manual:

You are Caleb, and you are a bad, bad man. You sold your immortal soul
for The Dark God, Tchernobog, and you and the other Chosen served Him
dutifully until He decided it was time to take everything from you for
Himself... apparently, even gods make mistakes.

Leaving you to rot in a grave and forgetting about you was a BIG one.
