How about something like:
Puzzle Box
5
Artifact
If you paid G in Puzzle Box's mana cost, put a 1/1 squirrel creature token into play. If you paid U in Puzzle Box's mana cost draw a card. If you paid R in Puzzle Box's mana cost, Puzzle Box deals 2 damage to target creature. If you paid B in Puzzle Box's mana cost target opponent loses 1 life and you gain 1 life.
0: Return Puzzle Box to its owners hand, play this ability only as a sorcery.
I changed the red ability because as Matt said the red and black were too similar.
Fourth, why exactly does white not get invited to the party?
Matt, does it really need to be any more complicated?
