For the wandmaker, we can decide to keep the drop (embers, rotberry, dust) which have some uses and makes for some interesting gameplay. I like this, it gives you some options if you don't like the wands he offer.
I would like to see something similar with the imp. Here's my suggestion: Instead of collecting 4-5 tokens, he just asks for 1 "ring essence". Instead this essence have a 20% chance to drop. Or possible 0/0/0/50/100% drop chance for each kill to keep it consistent with 4-5 kills.
If you keep the drop, you can use it to upgrade an existing ring +1 at an alchemy, or +2 at the blacksmith, costing some favor. Imp at floor 20 would appear once the essence have dropped, regardless of quest completion. But he could be grumpy and charge an extra +10% in his shop.
Using this essence would also curse the upgraded ring. Alternative is that the imp shows up as soon as you try wear the ring, throwing a curse on it in spite.
This would add some interesting new gameplay
- You get the ring as normal, everything essentially as before.
- You lose out on a potential +4 ring, but you can't escape that the upgraded ring you get, one way or another, to be cursed.
- For a +2 ring, it would also cost you additional time and favor.