Yagrum Bagarn is a resident of the Corprusarium, and the last known living Dwemer. He is infected with Corprus, and can only move around with the help of a modified Centurion Spider's lower half. He is a good friend of Divayth Fyr, a powerful, ancient mage who owns the Corprusarium and Tel Fyr. Yagrum is also the author of Tamrielic Lore.
During the First Era, Yagrum Bagarn was a Master Crafter working for the Dwemer Chief Tonal Architect Kagrenac. During the activation of the Numidium by the Dwemer causing his entire race to disappear, Bagarn was in Oblivion at the time and was not affected.
He later returned to Nirn and went to Vvardenfell. At some point he contracted Corprus, which caused his body to deform and bloat and went under the care of Divayth Fyr. He still researches about what happened to his race.
Later, if necessary, he can activate the Wraithguard if the Nerevarine has a reputation of 20 and Bagarn has a disposition of 90, or just a reputation of 30, or the documents "Dagoth Ur's Plans" and "The Plan to Defeat Dagoth Ur" (which are in the same room as Vivec—thus easier to obtain than the non-working Wraithguard). He will also need Kagrenac's Planbook and Kagrenac's Journals, since he is not an expert on the Wraithguard's use (although he helped create it). Once the requirements are fulfilled, the Nerevarine will need to equip the Wraithguard (and will be hit for 201-225 damage the first time it is equipped).
He is one of only two people in Vvardenfell who can readily translate Aldmeris (the other being Baladas Demnevanni). After translating the books The Egg of Time and Divine Metaphysics, Bagarn says that he would ordinarily explain in detail the theories presented in the books, but believes that Kagrenac's ideas must die as their master has.
Bleak Existence: "Since the disappearance of the Dwarves, I have been alone in this world, trapped in this grim prison. I can scarcely move. And my fellow inmates are scarcely good company. The risk of corprus disease deters most visitors. But if you meet with cultivated minds undaunted by the terrors of the Corprusarium, you might mention your recent interview with the Last Living Dwarf."
Divine Metaphysics: "This book is just an explanation of some of Kagrenac's theories. I could spend hours explaining them to you, but Kagrenac is dead, and I believe his theories must die with him."
- (With Divine Metaphysics) "By refreshing my memory with "Divine Metaphysics," I believe I can explain. The Dwemer were not unified in their thinking. Kagrenac and his tonal architects, among them Bthuand Mzahnch, believed they could improve the Dwemer race. Others argued that the attempt would be too great a risk. The war with Nerevar and the Dunmer may have led Kagrenac to carry out his experiments prematurely. Although this book argues that nothing disastrous could result, the disappearance of my race argues otherwise."
- (Without Divine Metaphysics) "I had not seen this book before, but it reinforces some my own theories. If you were to find more books like this, bring them to me and perhaps I could tell you more."
Gracious Keeper: "I owe my life to Lord Fyr. He took me in when I was a mad monster, out of my mind. In time, I emerged from my dementia, and now I am quite lucid most of the time, though my body is still a grotesque and useless prison. And I still have some feeble hope of cure. Lord Fyr has tried many spells and potions. None have helped me, but neither have they harmed me. If anyone can cure this disease, Lord Fyr can."
Hanging Gardens: "Yes, this book is written in both Aldmeris and in Dwemer. Many books were written in both languages in the days of Resdayn when Dunmer and Dwemer ruled together peacefully. I'd offer to translate, but this is really just a boring travel guide. If you find any other books in Dwemer, I could translate them for you."
Kagrenac's Journals: "Kagrenac recorded every step in his manufacture and testing of enchanted items. His journals will record any modifications or enhancements made to his original designs. I don't know where his journals might be. I am fairly sure they haven't been discovered, or Divayth Fyr would have heard, and would have told me. That suggests they remain to be discovered in some Dwemer ruin here on Vvardenfell."
Kagrenac's Planbook: "Kagrenac carefully planned all his projects in advance. His planbook will have all his original designs. I don't know where the planbook might be. I am fairly sure it hasn't been discovered, or Divayth Fyr would have heard, and would have told me. That suggests it remains to be discovered in some Dwemer ruin here on Vvardenfell."
Last Living Dwarf: "This is how I style myself. I do not know for a fact that I am the last. But in my travels thousands of years ago. I never encountered another. And since I have been here, I often ask Lord Fyr, but he says he has never heard a credible rumor of another Dwemer, on Tamriel, or in any Outer Realm."
My Race: "Once I was a Master Crafter in the service of Lord Kagrenac, chief architect of the great Second Empire freeholds, and the greatest enchanter of his time. I could not match the genius of Lord Kagrenac, but what he could envision, I and my colleagues could build. All of that is gone forever. I still retain my cunning, but my hands and eyes fail me, and my memories have long faded. My only consolation is each day to mock the gods who destroyed my race, and condemned me to this bleak existence."
Tales of your exploits: "A remarkable story. A pity to have to destroy Kagrenac's enchantments on the Heart. It would have been interesting to study them."
Theories: "Lord Kagrenac, the foremost arcane philosopher and magecrafter of my era, devised tools to shape mythopoeic forces, intending to transcend the limits of Dwemer mortality. However, in reviewing his formulae, some logicians argued that side effects were unpredictable, and errors might be catastrophic. I think Kagrenac might have succeeded in granting our race eternal life, with unforeseen consequences -- such as wholesale displacement to an Outer Realm. Or he may have erred, and utterly destroyed our race."
- While a sentient being, Bagarn is still technically a creature. As such, he is affected by certain spells and can be soultrapped.
- Killing Bagarn will cause Divayth Fyr to become hostile permanently.
- Bagarn has three lines of recorded voice dialogue, none of which made it into the game. They can be found with the Construction Set.
- It is possible Yagrum and Falion's paths crossed at one point, as Falion said he has met Dwemer. This may be possible as they were both travelling in Oblivion.
- He bears a slight resemblance to an X-Men villain named Mojo.