Chandler

is a member of the Demon Clan. He is Meliodas' former master.

Appearance
He is shown to be a short old man wearing a set of clothes and rings suited for nobles with elaborate designs. He has spiky hair, beard, and mustache in light color and his demon mark is on the right side of his head that has two spiked circles connected by a line from above to below his right eye. When he opens his mouth, he shows himself to have a full set of fangs for teeth.

Personality
Chandler is very attached to his former student, Meliodas, so much so that unlike the other members of the Demon Clan, in particular Estarossa and Zeldris, he completely disregards the betrayal Meliodas committed towards the Demon Clan 3,000 years ago. He even goes as far as to say that the original Elizabeth had kidnapped Meliodas even when it's known that his former student betrayed his clan out of love for her.

His high respect for Meliodas is as such that he berates anyone else who speaks lowly of Meliodas and would even cry crocodile tears if the subject of his student was brought up. His attachment to the Demon King's first son is shown when he immediately flew to Meliodas' location at the Boar Hat when Zeldris mentioned the Seven Deadly Sins were arriving and threatened to kill any obstacles in his way of rescuing his student.

History
Long before the Holy War 3,000 years ago, Chandler was the one to who instructed Meliodas in combat before his eventual betrayal of the Demon Clan.

3,000 Years Ago
During the Holy War, Chandler along with his clan was eventually sealed away within the Coffin of Eternal Darkness by the Allied Clans (Goddess, Giants, Fairies, and Humans).

Current arc
After Zeldris claims that he is the most worthy to be the next Demon King, Chandler, along with Cusack, comes into the scene. After Zeldris and Cusack's conversation, he tells him of his jealousy because Cusack gets to see his student. It is then revealed by Cusack that Chandler is Meliodas' former master.

Abilities and Equipment
As Meliodas' former master, Chandler is an extremely powerful demon. Zeldris states that along with Cusack, he is more than enough to fill the nine vacant spots of the legendary Ten Commandments.

His enormous power is shown as when he reached the Seven Deadly Sins his magical power shrouded the entire region they were in within complete darkness with Diane believing that night had suddenly fallen over them. Zeldris had even believed that Chandler can defeat if not kill all the Seven Deadly Sins excluding Meliodas on his own as well.

Like the members of his clan, Chandler possesses the black mark that allows him to manipulate darkness for various purposes like flight and regeneration. Unlike most of the Demon Clan when Chandler takes flight, instead of sprouting wings of the black darkness, his body is shrouded in an aura of darkness of which he can fly at incredible speeds as he reached the Boar Hat from several kilometers away in little time.

His saliva possesses incredible acidic properties as they were able to melt and dissolve the concrete floor of Camelot's castle and warrant Cusack to dodge them instead of enduring them.

Weapons

 * Staff: Chandler carries with him a wooden staff when he walks and is seen pushing it towards those he's berating like Cusack. Though he has yet to be shown using it as a weapon.

Meliodas
Chandler seems to love his disciple Meliodas very much. He is constantly obsessing over Meliodas a lot as is seen grovelling at the sight of Meliodas inside Perfect Cube.

Zeldris
We also have not seen any interaction between the two demons apart from Zeldris ordering him to rescue Meliodas.

Cusack
Chandler seems to get along well with Cusack as they talk and walk casually together. We do not know their history but it seems they have a mutual relationship. He does seem envious of Cusack as he had a "touching" reunion with Zeldris in good terms. Chandler however dislikes it when Cusack speaks lowly of Meliodas in spite of his former student's betrayal of the clan.

Elizabeth
Chandler has a intense loathing of Elizabeth, calling her a wench and blaming her for Meliodas' betrayal. When he saw again within the Perfect Cube with Meliodas, he threatened to kill her with a malicious smile.