Poseidon, Ocean God

To invoke this creature, sacrifice another creature
you control.
{t}{2} Create two siren 1/1 creatures.
{t}{3} Put an invocation counter on this creature.
{t} Remove three invocation counters from
this creature: Create a Sea Monster 5/5 creature.
"Poseidon emerged to the surface and saw a
huge ocean in front of him: his new home"