Twenty years ago today, a new STRAIN of demons was unleashed on the universe.   STRAIN was the first WAD I ever played that wasn’t just a pack of maps; it was a project that genuinely tried to be a proper sequel to Doom II. New weapons, new enemies, and a new story. And, for me, it is that proper sequel. Whenever I think about the Doom series, or tell people about it, STRAIN is just as much a part of it as Final Doom or Doom 64.   Quite a while back, Charlie Patterson (who le