Add some special rooms with unique monsters when mining.
Boss/eq npc in merchant mines with some sort of unique random eqs would be a
great addition to resources that all merchants grind whole day.

That would make merchant a bit more appreciated these days.. and exciting too

toper

Minecrafting usually gives you an abandoned mine once per boot. It has an
explorable area in base of mine with a boss mob of 2k-20k that drops a treasure
map which needs to be tracked down and dug up.