He can be obtained as a reward for the Black Book quest Untold Legends.
He can only be summoned using the Black Market power. When activated, he appears and offers to trade much like a regular merchant would. He will buy any type of item, except stolen items, and he sells armor and weapons based on the Dragonborn's level at that moment. He has 2,000 available for trading, which resets after two days.
- Ah, a fresh mortal to bargain with.
- Ah, sweet Oblivion. Soon I shall return.
- I do so love dealing with mortals.
- Until you summon me again.
- So, we meet again.
- So soon? You must be hungry for a deal.
- You have many things I wish to buy.
- I'm sure we can strike a bargain.
- Haggling with you can be so...entertaining.
- Let's make a deal.
- I can hardly wait.
- The Merchant will refuse to do business if summoned while trespassing. Leaving the trespassed area will alow bartering again, but his gold will be set to 0. After approximately 2 in-game days his gold will replenish.
- The Dremora Merchant is not affected by the Master Trader perk.
- Despite having no dialogue option to invest gold in his inventory via the Investor perk, after obtaining the Fence perk in Speech, the Dremora Merchant will purchase stolen items from the Dragonborn.
- Sometimes when trying to sell anything to him, the item will be removed from the inventory, but he will not give you any gold in return. Waiting for him to disappear and then summoning him again does not appear to fix this eithier.
- Sometimes when summoning him, he will have no items and 0 septims. To fix this simply wait for him to despawn and wait a few seconds, then summon him again. (This is caused by summoning him, selling off your loot, waiting 48 hours for him to respawn his gold, and trying to summon him again. Most likely occurring when deep in a dungeon and not wanting to leave, but having a lot of loot to unload. To fix, simply walk a few steps, wait an hour, and re-summon).