Kill him to get his bell, then bring it back to the Twins in Roundtable and hand it over. This will let the Twins sell everything that he was selling.
This works with every merchant in the game. As a rule of thumb (with the exception of our imprisoned friend here), kill only the merchants with donkeys. You have zero reason to keep them alive, and even less reason to come back to the middle of no where to purchase from them again.

Drops his bell bearing when killed, like all the traveling merchants. You should definitely be careful though, since he spams frenzy fire magic when you anger him.

If defeated drops Imprisoned Merchant's Bell Bearing

Since he is in the middle of nowhere, it is better to just kill him to grab his bell so you can give it to the Roundtable maiden, allowing her to sell the same stuff as him in a much more accessible (and less risky) location. Be careful when you engage him, though. Spawns a blood assassin (same mob that you had to fight to reach him) when attacked, also has a huge health pool and his yellow crazyness spell hits a massive area in front of him, while also dealing huge damage.

Yeah, sorry buddy, I know your not here because you want to be, but i really want your stock at a more accessible location

Hardest boss in the game

super ****ing annoying that this guy is in the middle of a hell-zone and is the only infinite source of dwelling arrows

dam felt bad enough this was the only merchant i killed for a better location, they really made me feel guilty with some of those lines he says when you attack and kill him.

I don't care how inaccessible his vending location is. I refuse to kill this man. He is just too lovable.