Undinia, Ocean Queen

Flying, Hexproof, Lifelink, Haste.
Whenever a creature you control dies, each
opponent sacrifices 2 creatures.
{5}{u}{u}: Whenever a creature enters the battlefield, put a +1/+1 counter on Undinia,
Ocean Queen. If there are more than 4 creatures
of a common type on the battlefield, creatures
you control gain Lifelink, Flying and Haste.