You could also, for something completely pulpish and out there, have a lost tribe of Neaderthals appear deep in the Black Forest. Seeing as the Neaderthals were first "discovered" in Germany anyway, then the Black Forest wouldn't be too far fetched for a lost tribe.
If you wanna turn the horror dial to eleven, you could make them into a cannibalistic tribe; werewolf tribe; cthulu-tribe; neer-do-wellers from a local village who engage in very heathen rituals out in the dark, dank forests to conjure up...