Chronos, Timekeeper

Flying, trample
Chronos is indestructible.
Chronos' mana cost is equal to 15 minus the number of turns that have passed since the start
of the game.
{3}: Put a time counter on Chronos.
Remove a time counter from Chronos: Exile target permanent.
{t}, Remove five time counters from Chronos: Take an extra turn after this one.