Mimir, also known as the Smartest Man Alive and nicknamed Head by Kratos, is a Norse Mythology figure known for his knowledge and wisdom, as well as an ally of Kratos and Atreus. Until Odin imprisoned him 109 years ago, he was Odin's advisor and the ambassador of the Aesir Gods. In God of War, he is one of the three protagonists.
Mimir is polite and kind, though his sense of humor is an equally important aspect of his character. Even in his beheaded state, Mimir tries to make the best of the situation, seeing it as preferable to imprisonment, and as such tries to assist in any way he can. Mimir is well-versed in deities, monsters, civilizations, the Nine Realms, and famous figures of Norse Mythology, and he is eager to share all of his knowledge with God of War's Atreus whenever he is asked.
God of War: Ragnarok — Mimir's Mythological Background
As a member of Kratos and his son's traveling company, Mimir serves as a balancing force between them, teaching Atreus to use his abilities for good and frequently advising Kratos to be more open about the truth of his past. To that end, Mimir demonstrates that he is emotionally sensitive and aware of the potential impact Kratos' distant attitude toward Atreus may have. Still, he respects Kratos' wishes and does not inform Atreus himself.
He was also the first to notice the dark change in Atreus' behavior after he discovered his godly heritage, and he tried to instill the ideals that figures like Tyr stood for, such as using one's powers wisely and for good. When this change in behavior began to strain the already loose bond between Atreus and Kratos, Mimir did his best to address the situation carefully.
Mimir quickly proved to be a devoted ally and friend to Kratos and his son,
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