Deep Sea Dolphin (海王 ダルフィン dīpu shī darufin?, Runic: ᛞᛅᛚᛈᚼᛁᚾ Dolphin) is one of the five subordinate mazoku under service of Ruby Eye Shabranigdu, the ultimate king of darkness on the Slayers plane (above Shabranigdu lies the Lord of Nightmares). Out of all of the Demon King's subordinates, she is the one that we know least about. Her beast form is unknown.
Residing in the Demon Sea, Deep Sea holds up the south-east corner of the mazoku barrier in place before the destruction of Hellmaster Fibrizo. Little is known about her. There were rumors that she and Greater Beast Zelas Metallium were hostile towards one another; not only is this unfounded, but there is good evidence against it- the only known picture of Dolphin features her alongside Zelas Metallium. Slayers fanon also concocted similarly baseless assertions that Deep Sea Dolphin went insane following the aftermath of the Kōma War; this is also false.