Cryofrozen Leviathan

{t}: Add {u} to your mana pool. Put a heat counter on Cryofrozen Leviathan.
{u}{u}{u}: Sacrifice Cryofrozen Leviathan. Put a 6/6 blue Leviathan creature token onto the battlefield with a number of +1/+1 counters on it equal to the number of heat counters that were on Cryofrozen Leviathan. Activate this ability only if there are at least 5 heat counters on Cryofrozen Leviathan.