Jotun Colossi

Affinity for players (This spell costs {1} less to cast for each player involved in this game.)
Annihilator X (Whenever this creature attacks, defending player sacrifices X permanents, where X is the number of players involved in this game.)
Cumulative upkeep - Tap target creature. (At the beginning of your upkeep, put an age counter on this permanent. Then you may tap target creature for each age counter on it. If you don't, sacrifice it.)