I just played a run where I acquired two Rings of Haggler, which I presume must only happen one in every 10,000 games where you get to dungeon levels six through nine, or more when counting the majority where you die somewhere between levels one and five. The two rings didn't reduce the price for buying from the second merchant, however, so I sold one for 160 gold. :-(
It could be interesting to make the rings of haggler and thorns upgradable, to allow for new possibilities of being able to buy everything or going without armour and evasion for mending and a vampiric weapon.
Related to this, I wonder if options to make the game easier, but without a ranking being generated, could be added to allow players to explore and experiment on the latter stages of the game.
Like, for example, having a setting that the troll blacksmith doesn't just add +1 to an item but instead adds the combined bonuses +1 so if you got a +0 plate and upgraded it to +3 and then found a +3 plate you would end up with the blacksmith reforging them to a +7 plate and not a +4.
[Please move to a different forum if posted to the wrong one. Done! - Shadow Automaton]
I have managed to get 2 Rings of Haggler and 2 Rings of Thorns in separate games. I got the second Ring of Haggler almost right after getting the first! The second Ring of Thorns came from Hero's Remains in the 5th stage.