Mardu's Challenge

Start with this card in the challenge zone. At beginning of your upkeep put an age counter on it an roll a dice:
1/2 - Mardu's Challenge deals 2 damage to each creature you control and 2 damage to you.
3/4 - Put X 1/1 Creature tokens with haste into challenge zone, being X the number of age counters into Mardu's challenge.
4/6 - Until your next upkeep, creatures you control can't block.