Ithlok, BlackTide Leviathan

Islandwalk, Swampwalk
Whenever another Kraken, Leviathan, Octopus
or Serpent deals combat damage to a player, each opponent discards a card, mills three cards and
you draw a card for each creature put into the graveyard this way.
{x}{u}{u}: Tap X target permanents.
"Swim at your own risk."