Neptunium, Tyrant of the Seas

Cult of {u} (This creature costs {1} less to cast for each {u} in the mana cost of creatures you control).
Islandwalk, Indestructible
When Neptunium, Tyrant of the Seas enters the battlefield, attacks or blocks return target nonland
permanent to its owner's hand.
Whenever you cast a spell with a converted mana
cost 3 or greater, untap Neptunium.
Noncreature blue spells cost {1} less to cast for
each blue creature you control.
"The ocean is against you."