Mael「マエル」 is one of the Four Archangels of the Goddess Clan. During the Holy War 3,000 years ago, a certain person reforged Mael and everyone else’s memories, giving the Archangel a new identity as a member of the Ten Commandments and the second son of the Demon King, under the name of Estarossa「エスタロッサ Esutarossa」.
Estarossa is a very tall and muscular man and wears a yellow (blue in the anime) longcoat with gold (silver in the anime) gauntlets and boots. He bears a great resemblance to the wanted poster of Meliodas. He has silver hair and noticeable facial stubble. He also has the same demonic mark as Meliodas and Zeldris but unlike Meliodas, it is above his left eye similar to Zeldris.
After absorbing the Commandment of Truth, Estarossa’s appearance remains mostly unchanged except that his forearms and legs are covered in darkness, and he gains a spiked circle made of darkness on his back. Once he absorbs the Commandment of Reticence, he transforms for a second time with his entire body covered in darkness similar to that of Meliodas’ Assault Mode.
It’s impossible to read what he’s truly thinking or feeling, just like Meliodas…But what worries me the most is that inexplicable feeling of unease and discomfort that radiates from him…Like something’s out of place…I can’t figure what the source of it is… But regardless, he is a strange man.
— Cusack’s point of view about Estarossa
Estarossa seems to have a normally relaxed demeanor. When Meliodas appears and threatens the Ten Commandments, he doesn’t seem overly bothered by the situation. Beneath this aloof exterior, however, he has a very sadistic and cold side. He cites Meliodas’ former ruthlessness as one of the traits he used to admire most about him, and clearly takes pleasures in torturing his estranged brother as punishment for the betrayal of his own kind. He did, however, begin crying when killing Meliodas, implying that he does still feel love for his older brother.
Estarossa seems to enjoy fighting for himself. For instance, he claimed that he wanted to fight with his brothers for the Demon King’s throne, even though he confesses to not being interested in it. Consequently, it makes his motivations rather unclear as he does not put himself forward for the Demon King’s throne and rather prefers “gaining” Elizabeth instead. He seems to show some respect against strong opponents such as Escanor to whom he asked his name because he deemed it worth to keep in mind.
Zeldris implied that Estarossa may hunger for more power, as he warned him to not try stealing the Commandments they had to recover for himself. Furthermore, Estarossa himself had no qualms in proposing killing his fellow Commandments to acquire their special abilities more quickly, showing that he does not care at all for them apart from possibly Zeldris. This was proven further when he ruthlessly killed the petrified Galand just because it would take time to have Zeldris release him from his petrification. His hunger for power was later proven to be true by the fact that he would rather have all the Commandments for himself, rather than to give them to Zeldris or Meliodas.