Overwhelming Leviathian

Convoke (Your creatures can help cast this spell.
Each creature you tap while casting this spell pays
for {1} or one mana of that creature's color.)
Overwhelming Leviathan cannot be blocked
unless at least 1 creature blocking it has both
power and toughness of 6 or greater.
"We'll there's not common defense. How do you stop
a wall of scales, muscle and blubber bigger than a
building? You don't, its like a mean tide, you just
run to get out of the way."