Kel'thuzad

When Kel'thuzad enters the battlefield, destroy
all tapped creatures if you pay a black mana.
Then, tap all other creatures if you pay a blue
mana.
{t}, {u}{u}{u}: Put a freeze counter on all other
tapped creatures. Creatures with freeze counters
doesn't untap during its controller's untap step.
When Kel'thuzad leaves battlefield, remove all
freeze counters.