Cthulhu Dice by Steve Jackson Games

About Cthulhu Dice, from BoardGameGeek:

Serving Cthulhu is fun... except for all those other cultists out to get you. So get them first! Cthulhu Dice lets you drive your rivals mad... Very, very quickly. Players take turns rolling the big, beautiful, custom 12-sided die, embossed with tentacles, Elder Signs, and more. Destroy your opponents' sanity! Better yet, steal it. But watch out for Cthulhu – when he comes up, he takes sanity from everyone! Eighteen glass Sanity marbles are included. Lose all your marbles and you're mad. The last sane cultist wins... Unless everyone goes mad together. Then Cthulhu wins!