In Zoroastrian mythology, Mithra was a deity of contracts who was the protector of truth and the enemy of error. He was created by the supreme deity Ahura Mazda as the greatest of all Yazatas and an important aid in the destruction of the demonic forces led by Angra Mainyu (also known as Ahriman) in later Persian sources. He was one of the three Yazatas alongside Rashnu and Sraosha who judged the souls of the dead.
His main appearance is a lion-headed figure found in temples of Mithras in the former Roman Empire, often identified as god of the Mithraic cult named Arimanius. Some identify the figure as Zurvan, a primordial divinity of time and destiny, from an extinct branch of Zoroastrianism named for the deity, while others identify it as the Demiurge, Yaldabaoth. What is certain is that the lion-headed deity is associated with time and seasonal change.
In Vedic mythology, Mitra is a god of honesty, friendship, meetings and contracts despite his role as an asura (although he is sometimes addressed as a deva). In this way, he was often paired with the asuraVaruna where they were twinned as Mitra-Varuna. Together they were the gods of the oath and the most important Asura in the Vedic pantheon. Mitra was also another name for Surya.
He is not to be confused with Mithras of Roman origin.
Mitra is an extra boss found in the Northwest Tower of the Forest of Confusion. Upon defeat, he drops Lucifer's Armor, which can only be equipped it if the protagonist has 30+ Vitality and 25+ Intellect (including equipment bonuses).
"An ancient Iranian god of contracts, he was also worshipped as a sun god. At the end of time, he will descend from the heavens and raise the dead for final judgement."
—Shin Megami Tensei III: Nocturne compendium
He is one of bosses in the Diet Building, representing the power of the Assembly of Nihilo. He is confronted in the senate chamber. After his defeat, he can be fused as a regular demon, and is the only one to learn the unique skill Death Pact, a conversation skill with a high recruitment rate and which has the power to occasionally inflict the Stone ailment on demons who refuse to join.
"A sun deity of Zoroastrian lore. He is the son of the god of light, Ahura Mazda. He is the sunlight that appears before dawn and has the power to expel darkness. He also has a fearful war god side to him; those who opposed him would have their bones crushed."
In Fornax, Mithras is one of the four demons to swear vengeance upon the protagonist for defeating him in Sector Bootes, shedding his original shape and revealing himself as the lion-headed Mithra, though despite the power boost he is still defeated. Both of them can be fused through the Demonica with special fusion.
"An ancient Persian god of contracts, who was also revered as a sun god who brought harvests when he was introduced to the Zoroastrian religion."
—Persona 5 background
Mitra is the sixth Persona of the Temperance Arcana and can only be obtained through fusion in the Velvet Room. He is the first Persona usable in battle by the protagonist to learn the Kouga skill and the first Persona to learn Thermopylae. Mitra is also one of the three Personas to learn Mahama and Bless Boost When itemized through Electric Chair execution, Mitra produces the Death Contract axe for Haru Okumura, which has 140 ATK, 86 ACC and add the Despair (low) effect to Haru's attacks. Mitra is one of the Personas needed to summon Sraosha through advanced fusion.
In Devil Survivor 2, Mithra is a unique demon that doesn't require a particular fusion combination to create. Instead, the protagonist has to achieve a Fate level of 3 with Yamato Hotsuin before it is available. Once this has been achieved, it is unlocked for fusion on all subsequent runs as long as the previous save is imported..
"A god of the sun and war in Zoroastrian lore, and also recognized as the god of contracts and fraternity. He punishes those who are corrupt and is known to cure disease, sustaining harmony and truth on earth."
When fought as a boss, whether it be as Mithra or Mithras, he will abuse Waking Dream which has a chance percentage to cause Strain status on the opposing party. After a few turns have elapsed from that action, he will use Light of Order, an attack with a 100% chance of instant kill. Mithra will mix in a few physical attacks to separate the frequency of his unique skills, but he will otherwise follow a consistent attack pattern.
His artwork since Shin Megami Tensei III: Nocturne seems to resemble the lion-headed figure found in temples of Mithras in the Roman Empire.
Also in Shin Megami Tensei III: Nocturne, Mithra serves under the Assembly of Nihilo, whose mastermind turns into Ahriman.
His design as Mitra Bosastsu draws inspiration from both his and Mithras origin, having bull traits that stem from Mithras, angelic wings and gold/white to his angelic Yazata origins and a Bodhisattva due to a believed Vedic origin in Mitra and Miroku/Maitreyas name.
Despite him being one of the three major Zoroastrian Yazatas with Rashnu "Justice" and Sraosha "Obedience," he never appears as a member of the Seraph race.