Monspeet

is a demon who is a member of the Ten Commandments, a group of elite warriors of the Demon Clan handpicked by the Demon King himself. He was sealed away along with the rest of the clan in the Coffin of Eternal Darkness until he was set free by Hendrickson.

3,000 years ago
Along with the rest of the Demon Clan, Monspiet was sealed away by the Goddess Clan after losing the Ancient War against the Four Races (Human, Fairy, Giant and Goddess Clans).

Current arc
After Hendrickson managed to remove the seal, Monspiet and the rest of his fellow Demon Clan members appeared before the terrified former Great Holy Knight and Fraudrin in Dreyfus' body with Zeldris uttered Meliodas' name as if he knew him. After being informed by Fraudrin of the current events in Britannia, Zeldris suggested that they should head for Edinburgh Castle for recuperation of their severely drained magical powers due to the seal they're trapped in, which everyone agreed and left Zhuhur Valley by flight, leaving a terrified Hendrickson.

Arriving at Edinburgh Castle, Monspiet and his fellow Ten Commandments find it in ruins and concludes that it was Meliodas who caused the destruction of the castle as if there was a great battle fought there.

Abilities/Equipment
Like all members of the Demon Clan, Monspiet possessed a Black Mark similar to Meliodas, utilizing the mysterious jet-black matter as shown forming wings for flight and as a member of the Ten Commandments, he may be exceptionally powerful. His aura is so powerful that made the normally calm Hendrickson sweat in fear of their mere presence.