A UAC facility somewhere in the Pacific didn't report in lately. You are sent to investigate and find that hell broke loose there (What else would you expect). But instead of turning and running away in horror you go in and take them on...
Ben Morris for DCK, id for DooM and many WAD Authors for inspirations
New level from scratch
I hope there aren't any. If so, it's probably some texture I forgot to replace or properly align. There shouldn't be anything bad like HOM or such, though.