Ocato of Firsthold, also known as Battlemage Ocato, High Chancellor Ocato, and later Potentate Ocato, was an Altmer battlemage at the center of politics in Tamriel for decades. After Jagar Tharn's treachery was discovered and he was defeated in 3E 399, Ocato was appointed as the new Imperial Battlemage, a position he would hold contemporaneously with his long-held seat on the Elder Council. By 3E 427, he had become Chancellor Ocato, and by the end of the Third Era in 3E 433, when the Emperor and his heirs were assassinated, Ocato had become Lord High Chancellor of the Elder Council. When he could not bring the Council to choose a new Emperor following the end of the Oblivion Crisis, he reluctantly accepted his role as de facto ruler and became Potentate Ocato. Roughly a decade later, when Ocato was on the verge of successfully re-stabilizing the Empire, he was assassinated, most likely by the Thalmor.
He was likely slain some time in the Merethic Era, perhaps during the Dragon War, although his soul was not devoured. Like many dragons, his remains were retrieved by members of the Dragon Cult, and he was buried in a dragon mound near the Skyrim city of Riften. The location of his grave was discovered through interrogation of Dragon Cultists by the Akaviri Dragonguard, and was later documented by the Blades in 2E 373.
In 4E 201, Odahviing was returned to life by Alduin and became his ally. After the Last Dragonborn failed to defeat Alduin on Mundus, Odahviing was targeted for interrogation. The Dragonborn called his name through the use of the thu'um, which dragons perceive as a challenge. By following the call, Odahviing was lured into Dragonsreach, the castle in Whiterun which was used by King Olaf One-Eye to imprison the dragon Numinex in the First Era. With the help of the Jarl of Whiterun, the Dragonborn used an ancient dragon trap to capture Odahviing. Ensnared and defeated, Odahviing spoke with the Dragonborn and revealed that Alduin had retreated to Sovngarde. In return for his freedom, he agreed to bring the Dragonborn to Skuldafn Temple, an ancient ruin located high in the Velothi Mountains reachable only by flight, where a portal to Sovngarde was located.
After Alduin's defeat in Sovngarde, Odahviing allied himself with the Dragonborn and provided aid in battle when called. He was uninterested in the Way of the Voice, and thought that Paarthurnax was foolish for trying to convert the remaining dragons to the philosophy. Odahviing remained at the Throat of the World, seemingly of no great concern to the reformed Blades.
King Olaf One-Eye was a First Era Nord Jarl of Whiterun (and later High King of Skyrim) famous for imprisoning the dragon Numinex within his palace, which was dubbed Dragonsreach in honor of this feat. Olaf purportedly confronted the dragon with some of his troops on top of Mount Anthor, where he used the thu'um to aid him in a duel which ended in Numinex's defeat. Olaf then conveyed the dragon back to Whiterun where he imprisoned it in his castle, dubbed Dragonsreach in honor of this task. Numinex was purportedly imprisoned there until his death.
Due to his fame, Olaf was eventually named High King of Skyrim. However, his reign, which started in 1E 420 and lasted 32 years, saw its share of controversy. Notably, the bard Svaknir wrote a scathing verse decrying him as a fraud and a tyrant. Olaf responded by imprisoning the bard and destroying every copy of the verse which could be found. Ancient bard texts, perhaps inspired by Svaknir, claimed that Olaf and his men came upon a weakened Numinex and captured the dragon without significant effort, and fabricated the orthodox tale to ensure his place as Jarl and possibly to aid in his bid to become High King. An effigy of Olaf is ritually burned in Solitude as part of an annual festival known as "The Burning of King Olaf". However, Olaf is still remembered in Skyrim for reuniting the province after the War of Succession and for conquering the Reach. For more information, see the lore article.
 Olmgerd the Outlaw (?b - ?d)
Bastard son of Harald Hand-Free. He and his brothers Hjalmer and Vrage the Gifted ruled over the First Empire of the Nords after their father's death in 1E 221. He fought and died in present-day Morrowind, where he was buried "as befits a Nord lord's son": on his ship, in the Tukushapal caverns, with his riches and his enchanted axe named Stormkiss.
 Saint Olms the Just (?b - ?d)
Patron of Chandlers and Clerks. Founder of the Ordinators, Saint Olms conceived and articulated the fundamental principles of testing, ordeal, and repentance. One of the cantons of Vivec in Morrowind was named in his honor.
 The Oracle (?b - ?d)
The Oracle is a wise woman and a seer who lives in the Dragontail Mountains. Although she is blind, she is rumored to be the wisest woman in Tamriel. She gave her eyes to the gods, which gave her the power to see the future by looking through their eyes. By tradition, she has been the Chief Counselor to the monarchs of Sentinel. She advised King Camoran against warring with Daggerfall, foreseeing his death during the War of Betony. She also acted as a confidant of Queen Akorithi during her reign. The Oracle often contacted the Mages Guild through her Acolyte when she foresaw an attempt on the life of an uncooperative noble, whose death would cause havoc in the region. The Daggerfall Chronicles was hidden in a shrine to the Oracle after it was stolen from the Scenarist Guild.
 Oreyn Bearclaw (?b - ?d)
Son of King Faume Toad-Eye, Oreyn Bearclaw was a respected clan hunter and a future leader who was one of Valenwood's most legendary heroes. Bosmeri legend claims Oreyn single-handedly defeated Glenhwyfaunva, the witch-serpent of the Elven wood, forever bringing peace to his clan. Oreyn would go on to accomplish numerous other deeds, but eventually lost his life to the Knahaten Flu. His Helm stood as a monument of his stature for future generations to remember. Some claim that many of the deeds Oreyn was made famous for were actually done by his Orc companion, Kharag Gro-Khar.
King Orgnum is the immortal wizard king of the Maormer who resides on the continent of Pyandonea. He is famous for his coffer. Throughout his reign, he has constantly assaulted and raided the Summerset Isles and filled his coffer with the land's riches for eras.
In the Third Era, Orgnum began the War of the Isle when he invaded the Summerset Isles. He visited Queen Potema in 3E 110. Orgnum very nearly succeeded in conquering the Summerset Isles, and would have were it not for a freak storm that destroyed his entire fleet. This storm is usually credited to the Psijic Order.
 Orvas Dren (?b - ?d)
 Baron Othrok (?b - ?d)
Baron Othrok was a Baron of Dwynnen, who ruled the area in the middle of the Third Era. Although the Baron definitely existed, it is difficult to separate the truth from legends that have arisen around him.
One legend deals with the foundation of the Barony itself, and how in 3E 253, the Baron led an army of animals and men in a victory against the undead armies of Castle Wightmoor at the battle of Battle of Wightmoor. Whether this is literally true or not, the people of the Barony celebrate a holiday called Othroktide on the 5th of Suns Dawn each year as a memorial to the battle.
The Baron is even more famous as the man who stopped the invasion of the Camoran Usurper in 3E 267. Although the credit given to the Baron is probably overstated, it was at the Battle of Firewaves, not in Dwynnen itself but nearby, that the combined armies of Dwynnen, Ykalon, Phrygia, and Kambria defeated the Usurper and restored peace to Tamriel.