The Isle of Isthilnoc

{t}: Add {u} or {s} to your mana pool, then put a Slumber counter on this card.
If this card has 10 or more Slumber counters on it, exile this card, then create Isthilnoc, a legendary 0/20 blue Dragon Turtle creature token with, "This creature can block all attacking creatures your opponent controls. Creatures blocked by Isthilnoc don't untap during their controller's untap steps."