Hmm, I can't think of any recent creepy adventure games that work on a PPC Mac. Older titles that fit into that category are Rune (OS9), Sin (OS9), Alice (OS9/OSX) and Klingon Honor Guard (OS9), Dark Vengeance (OS9), Heavy Metal FAKK2 (OS9) and Quake III (OS9). Most of these work in Classic, at a slightly slower speed. Check out the reviews here http://www.insidemacgames.com/