Favorite Monster - Immortal/Outsider

Ice, ice baby! As in Ice Devil (or Gelugon, if you prefer). I know there are more powerful demons & devils out there, and the various lords and named beings are iconic, but the ice devil has always struck me as an otherworldly terminator, if you will. Cold (no pun intended), remorseless, brutal, efficient killing machines from hell! The illustration from the 1E Monster Manual has got to be one of my favorite all-time black & white creature pictures.