Door of Time

Indestructible
{t} {x} : Exile a creature you control. On your next upkeep, return that creature to the battlefield under your control with X +1/+1 counters on it. Use this only during your main phase.
{t} {x} : Exile a non-creature spell from a graveyard and add X counters to it. At the beginning of your upkeep, add one counter to the exiled card. If there are 6 counters on that card, you may cast it without paying it's mana cost.