Underhell is a Source Engine game developed by the Underhell Team in collaboration with We Create Stuff. Underhell Chapter 1 requires ONLY Source SDK Base 2007 installed. No Source game is required.
This is the best HL2 mod i have played as of yet.
-Great gameplay with features rarely found in source games.
-A story that is well crafted and immersive.
-And very good mapping and modelling.
I hope the next chapter will be released soon, I really cannot wait to see what will happen next.