Custom Scroll/Potion/Staves Mob
"What do you want on your scroll?"
Pick:
Armor, Detect Invis, Giant Strength, etc
"Oh, Armor and Giant Strength, eh?"
"Well, that might cause ye to choke a bit, possibly lose your voice," (causes Silence)
"Ye still want it?"
Confirm/Pay
Bam! You have a potion tailored to your needs.
Obviously, this is a loose idea. It could be a mob in a special area or just an adjustment to the merchant mobs.
I dunno, just sounded neat to me.
Damn. I thought this was going to be about a restrun demon [Turnip] Hero 
I like the idea.
Game mechanic wise - we want certain things to be difficult to attain. Having a mob that can make it easy to farm scrolls at anything less than an obscene amount of gold would tip things even further in the favor of mages and hybrids.
Well, not just scrolls. Potions too. Also, it has a built in drawback. Obviously, the list would not include Sanctuary and Flight and whatnot. Certain combos can be limited as "too volitile" or "too wordy" etc. It could be like:
Choose the primary function:
Protection, Strength, Agility, Healing
(Protection) What shall I brew? scribe? enscript? (etc)
Armor (200), Stone Skin (800), Protection Good (1000), Protection Evil (1000), Sanctuary (10000)
Each pick would run up a tally, then you pay it and viola! A nice potion just as you want it. As said, it could have drawbacks, like:
"Might make you choke a bit" - Silence
"Might cause a big headache!" - Thunderclap
"Oh! That one might hurt going down!" - Cause Critical
"Don't take that and operate large seige equipment" - Enfeeblement
Etc etc. This could be a new type of arrangement even, instead of potions or scrolls or staves, etc. It could be Tablets or "Concoctions". Each city could have a Master Alchemist that does this.
Anyhow, just a thought.
This wouldn't be for every mob in the game to convert to, as it is distracting and takes a while to get a simple potion. It does, though, add some flavor to specific mobs (perhaps a new Gnome mob in Tarandue at first can do this, then if it works out, other mobs randomly spread around the realm).
Game mechanic wise - we want certain things to be difficult to attain. Having a mob that can make it easy to farm scrolls at anything less than an obscene amount of gold would tip things even further in the favor of mages and hybrids.
I think this is a great idea. I would further suggest a limit to any one type in the inventory at one time.
(has 5 protection pills)
"Sorry, you have to let the other guys buy some too."
"dang"
I think it would be much more friendly to game mechanics if you handed him a vial and a detect invis potion and he gave you one that did both.