Great Demon Lord

The, or Beelzebub III, is the Demon Lord of the entire Demon World. He is a former ruler of one of the Demon World's countries prior to its unification, thereby being a member of the Seven Deadly Sins.

Appearance
The great-demon lord seemed to always use a helmet with a pair of horns on its sides and has long green hair along with a black cape. He appears on screen taken from an angle behind him, rarely having his frontal view seen. In Episode 53, it can be seen that he keeps a long fringe that masks his face, hence keeping the mystery revolving how he looks like intact.

Personality
The Great Demon Lord is a very stupid and forgetful king of Beezlebyute, and he wants to destroy the Human World because they breed like roaches. He also forgot his wife, Iris, and hangs out with other girls. He loves to sing karaoke, he is also the father of both Lord En and Beelzebub IV

History
The Great Demon Lord was once a ruler of one of the Demon World's countries. However, he would eventually unify it and become the sole ruler of the entire realm. His reign as Demon Lord was challenged once when Lucifer, also a former ruler of one of the Demon World's countries, fought against him for possession of the royal throne. Though he was victorious, the conflict led to great turmoil in the realm.

Mobichi Arc
Behemoth mentions that he made a contract with the Great Demon Lord, though he does not expand on what they are. However, according to the contract that they made, the tissues that the Great Demon Lord sent to Tatsumi Oga were made to summon a Demon from Behemoth's Pillar Division after a specific ritual is made.

America Arc
While Hilda was temporarily in the Demon World, the Great Demon Lord gave her an item that she was supposed to bring to his wife Iris.

Powers and Abilities
The Great Demon Lord has the power to create artificial demons like Tamapochi. It is currently unknown how he creates them. He has similiar ability with beel's zebul finisher since it is said to be the overlord's special skill but it is unknown how a demon could use an emblem technique like a spellmaster.

He is the father of Baby Beel who he send in his place (because of a Majhong Tournament) to destroy the human world. He is also very strong, easily beating up Takamiya and Fuji and has been stated by them by being very powerful despite them being Satan and Lucifer contractor.