Yryn, Trailblazer

Window 6 (If you have taken 6 or more turns this game, you cannot cast this spell from your hand.)
At the beginning of your upkeep, put two -1/-1 counters on Vryn, Trailblazer.
{r}{r}{g}{g}: You may cast Yryn, Trailblazer from exile until end of turn.
Players cannot win or lose the game.