Caligo is a middle-aged stout man with dark hair and eyes. He wears the brigadier general army of Niflheim. He and Loqi Tummelt have the same suit of armor but with different crests; the one on Loqi's is the one that appears on flags carried by magitek infantry that drop from landing craft and is in display in the imperial-conquered areas of Lucis. The robed figure from the crest on Caligo's armor appeared on flags in Episode Duscae.
Caligo is arrogant and cruel. His arrogant attitude is in full form when the party confronts him and his forces in Formouth Garrison, taunting the party during the attempt to capture them.
During the Dawn trailer Caligo appears to roughly handle and throw a young Lunafreya Nox Fleuret to the ground. If the trailer is canon, this is assumed to have happened after the Fenestala Manor was captured by Niflheim, as they are inside the manor proper.
After Niflheim invades Insomnia, Caligo Ulldor is in charge of occupying the Lucian territories. He is present with Ravus Nox Fleuret, Aranea Highwind, and Verstael Besithia in a meeting with Emperor Aldercapt, who wants Lunafreya killed to procure the Ring of the Lucii currently in her possession. Verstael asks the emperor to reconsider, citing her power to commune with the Astrals, and refers to her being the "key for the King". During the meeting Caligo stands silent.
When Niflheim forces occupy Lestallum, Caligo interrogates Jared Hester, the chamberlain to the Amicitia household that worked for the Lucian royal family. Jared is killed in the confrontation, refusing to provide information on Noctis. Caligo later admits he acted "perhaps too hastily". Niflheim posits Jared attacked Ulldor from behind when he was patrolling the area outside Leville Hotel and he acted in self defense.
As revenge, Prince Noctis and his friends infiltrate Fort Vaullerey to take Caligo hostage. During the stalking, they overhear Caligo speaking to soldiers of his disdain of Commodore Aranea Highwind and Chancellor Ardyn Izunia, claiming that he is no fool, and he knows Aranea was sent to watch him. Noctis ambushes Caligo but he escapes, although injured. He is later released from an imperial hospital after receiving medical treatment and returns to Lucis to resume his duties.
When Noctis later infiltrates Formouth Garrison in Leide, Caligo and Loqi are there to usher the infantry upon him. Astonished by Noctis and his friends' power, they engage them in their magitek armors, but Noctis prevails and destroys the base.
After hearing that High Commander Fleuret had ordered a full scale assault on the sea goddess Leviathan, Caligo requests that his MA-X Aureus be outfitted with naval combat capabilities and to coat the mech in gold to reflect the accolades he has accumulated over the years.
As depicted in Episode Ignis, Caligo leads his magitek forces to conquer Altissia in the wake of Leviathan's Revelation. High Commander Nox Fleuret orders a retreat, but Ulldor protests as they have yet to capture the Ring of the Lucii. Ravus reminds him that only a Lucis Caelum can wield the ring, as he once tried to and lost his arm. After Ravus departs Caligo resists the retreat order, planning to get the ring for himself.
Ulldor runs into Ignis, one of Noctis's friends who had briefly captured him in Vaullerey. He is delighted at a chance for revenge and pursues Ignis through the town with his MA until Ignis is forced to fight back. During their battle, Ulldor tries to aggravate Ignis by asking him to beg for his life, like "that civilian" he had killed in Lestallum, referring to Jared. Ignis defeats Ulldor, who is mystified he could have lost. As he staggers out of his damaged MA, he is unceremoniously killed by Ravus, who impales him with his sword.
Ulldor is fought in his MA, MA-X Dux, during the sidequest Formouth Garrison.