It was on Netflix for a time....gone are those halcyon days. That Tangerine Dream soundtrack is immense.The keep is good horror, its a pity nowhere has it on streaming. Nearest thing to it is overlord. Which i enjoyed as it reminded me of return to castle wolfenstein game.
So many great films being mentioned, I'm also a sucker for the old J-Horror stuff as well. Some of that really gets under your skin.