Now more than ever, now that so many dwarfs follow the overworld paths to Ankh-Morpork and other such villainous places, do they fear the taint of the world above which leads dwarfs into dangerously undwarfish thinking: showing themselves as knowingly and unashamedly female, ignoring the wishes and commands of Grags, and seeing underneath the mountains as where old-fashioned dwarfs live.
All Deep-Downers have a Draht - an unique, glowing identity symbol - tatooed with vurm-blood under the skin. Most of them (such as Albrecht Albrechtson) wear clothes based on those worn by Knockermen: heavy leather outfits that make the wearer look like an upturned icecream cone, and with a flap across the face to be worn to shield oneself from the outer world.
If they have to venture above ground, they hide themselves from the sun, being carried on palanquins shrouded in heavy drapes so as not to be tainted by the touch of the sun.
Whilst highly regarded by many dwarfs, many others are beginning to see them as anachronisms and to feel slightly embarrassed by their beliefs and attitudes. This is a power-struggle being played out over many decades and between powerful factions. the current Low King, Rhys Rhysson errs towards listening to the Deep-Downers but not necessarily following their ideals.
The Deep-downers who live under Ankh-Morpork feel that they are not ruled by its laws or culture (in some ways similar to the Guilds and the University) as they claim Dwarf Law applies below ground, but Sam Vimes begs to differ and he has the rosewood and silver stick.
The Deep-Downers are faced down and somewhat humiliated by Low-King Rhys in Thud!. Evidently they spent the time plotting, as an even more militant strain emerges in Raising Steam, prepared to use violence to enforce adherence to the old ways. They are supported by their enforcers, the Delvers, previously encountered by Sam Vimes and his family underneath Ramkin Manor.