You could try [i]Lords of Madness[/i], it has a lot of Lovecraftian stuff in it. You might also want to look into [url=https://en.m.wikipedia.org/wiki/Call_of_Cthulhu_(role-playing_game)][i]Call of Cthulhu[/i][/url], a pen and paper game that sounds pretty much like what you're looking to turn your D&D campaign into, albeit with less combat. [spoiler]also its "The Dunwich Horror", not "Horrer" sorry, that was just bothering me.[/spoiler]