According to merfolk legend, a denizen of the deep swallows the horizon at the end of each day, bringing on the cold blanket of night.

Dominaria Remastered

Denizen of the Deep

When Denizen of the Deep enters the battlefield, return each other creature you control to its owner's hand.

When Denizen of the Deep enters, return each other creature you control to its owner's hand.

"Don't be silly, Grandfather. If the tides were caused by some monster drinking the ocean, wouldn't more ships go missing?"
—Leda, Vodalian youth

When Denizen of the Deep comes into play, return each other creature you control to its owner's hand.

When Denizen of the Deep comes into play, return all other creatures you control from play to their owner's hand.

When Denizen of the Deep comes into play from your hand, return all your other creatures from play to your hand.