Percy Jackson and the Olympians: Legends

Mimir, who is a severed head, appears to be an old man with many wrinkles, his has noticeable lateral canthal lines near the corners of his eyes as well. As for the rest of his head, Mimir adorns beautiful gold patterns magically etched into his horns when he went into Odin’s service, his golden bifrost eyes, gifted to him from the Giants, is one of his most notable features. Three years after Baldur's death, Mimir's appearance is largely the same, apart from his beard now being braided, with a few gold, gilded beard beads/rings woven into them. His head is covered in a multitude of runes, most from his service to Odin, the rope tied around his head is an Asgardian weave—enchanted for durability. Lastly, Mimir's severed neck stump has over time turned to a dark, blackish color. From Mimir's own comment he has revealed that when he still had a body, he had hooves.

Mimir is well-mannered, kind and possesses a cheery and witty, though occasionally sarcastic, sense of humor. Even in his beheaded state, Mimir tries to make the most of the situation, finding it better than imprisonment and as such he tries to be helpful in any way he can. Mimir has a wealth of information regarding the deities, monsters, civilizations, the Nine Realms and famous figures of the Nine Realms, which he will eagerly share with Atreus whenever prompted. Mimir is a master of diplomacy, though some like Freya and even some of the Aesir would state otherwise. Despite his bright personality, Mimir possesses a great deal of anger and resentment towards the Aesir Gods, Odin and Thor in particular. He finds a great majority of them to be hedonistic, paranoid, arrogant, warmongering and the ones to blame for the tragedies the Nine Realms have endured. The one exception is Týr, whom Mimir held in the highest esteem.

Mimir, formerly known as Puck, is a Celtic fae who became Odin's advisor and the ambassador of the Aesir Gods until Odin imprisoned him for 109 years. Hailing from a faraway land, Mimir was a faerie king's errand boy and unofficial jester. Frequently, Mimir and other faeries, nicknamed "Goodfellows", would walk amongst mortals to sow mischief and as long as his lord was kept amused, they were spared the consequences. Eventually, Mimir's king grew weary of his antics, forcing him to leave his homeland. At some point early in his service to the Raven King, Mimir forged an alliance between the dwarves of Svartalfheim and the Aesir of Asgard. This would ultimately work out to the detriment of the miners as Odin would use them for mass production of weapons for his Einherjar, and other mining materials, seeing to it that that the Dwarves mining skills were only used by Asgard.