Deepsea Stalker

Islandwalk
As long as there are ten or more creatures on the battlefield, you may put Deepsea Stalker from
your hand onto the battlefield without paying its
mana cost anytime as though it had flash.
When Deepsea Stalker enters the battlefield,
return all other creatures to their owner's hand
except for Krakens, Leviathans, Octopuses, and Serpents.