Take Spades, and add evil. The result is Die Sieben Siegel.
The game is a pretty standard trick-taking game. The cards are numbered 1-15 in five different suits, and red is always trump. If someone leads a color, you must follow suit if you can; otherwise, you can throw off a card or trump the trick. It's an exact-bidding game, but you predict your tricks by taking colored chips. For each trick that you win, you toss a chip back. If you take a trick in a color for which you didn't have a chip, then you must take a black chip (worth -3 points). If you have any colored chips left at the end of the round, they're worth -2 points. If you have any white chips left at the end of the round (wildcards that you get when someone takes a colored chip away from you during bidding), they're worth -4 points.
There's also the saboteur, whose role is to feed unwanted tricks to other players. Instead of bidding tricks he takes 4 black chips. When players take tricks they didn't predict they take black chips from the saboteur. If the saboteur can feed enough of the black chips to enough players, he can zero out his score for that round. He gets -1 point for every black chip he has left at the end of the round.
This is a mean-spirited game. Only play with people who can take it as such.