Leviathan

Leviathan (レヴィアタン) is advanced-level furniture created by Beatrice. Leviathan often speaks to Lucifer on behalf of the youngest sisters. At her best, she has a brutal, deeply envious nature and is adept at spotting people's weaknesses. However, she is usually nothing more than a selfish crybaby. For some reason, she's not a very quick thinker, and she often comes in last among the sisters, ends up with the short end of the stick, and cries.

Background
When the Seven Stakes of Purgatory were growing in their youth, Leviathan was the slowest to grow. Her envy of her sisters lasted seven days and seven nights, ultimately culminating in her envy giving her power eclipsing the rest of the stakes.

Banquet of the Golden Witch
In, Leviathan is called upon to kill Kyrie Ushiromiya.