Leviathan

The Abyssal Serpent Livyatan, sometimes known as Leviathan, is the Demon Lord that embodies over the sin of Envy and one of the Seven Princes of Hell that rules Hell and is considered one of the Devil's greatest sycophants. He is a fallen Chalkydri who accompanied Lucifer in his rebellion alongside the other legions of angels only to be banished to hell, becoming its gatekeeper. Livyatan, once known as Flumenel, was a Chalkydri, a monstrous sub-species of Seraphim, who was a disciple of Uriel, colleague of Gabriel and sycophant of Helel.