Esper'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 - Sacrifice a non land permanent
3/4 - put a legendary creature token with flying, vigilance, indestructble and "this creature power and thoughness is equal to half of Esper's challenge age counters, rounded down" in the challenge zone
4/6 - Until the next upkeep, you're not allowed to play spells.