A flash game series originally released on Newgrounds and created by Ben Leffler, who just loves to make creepy/scary-as-hell games, the Exmortis series A trilogy, the first game (found here) in 2004 and the sequel two years later (found here), with a closing chapter released as Shareware for Halloween 2009. The development blog is found here. And just for future reference, the first screen you see says that you should play with the lights off and the volume turned up. Don't.