Prayers of Armageddon is a Doom II megaWAD released in 2010 by Finnish Doomer "H3llraich", consisting of 33 levels, one only accessible via IDCLEV. It won't run in vanilla (or Chocolate) Doom, but it'll run in just about any other recent source port, at least as far as I can see. The story's setup may be different, but the result is familiar. Some scientist at a UAC teleportation research facility went nuts, killed his coworkers, and started bringing the hordes of Hell to your reality. You're tasked with finding the invasion's mastermind and putting an end to the ordeal.
