Kiora, Oceanic Avenger

This spell costs {1} less to cast for each Kraken, Leviathan, Octopus, and Serpent creature card
you own in exile and in your graveyard.
As an additional cost to cast Kraken, Leviathan, Octopus, and Serpent creature spells, you may sacrifice another creature. If you do, reduce that
spell's casting cost by the sacrificed creature's
mana cost. If you cast a spell this way, you may
put target nonland permanent on the bottom
of its owner's library.