They appear to be very dark, overly large worms - perhaps a handspan in length and half as thick as a finger. That and their matt, dull skin marks them as something other than a typical earthworm.
What do you mean, the little wriggly ones you throw at fish or the big rock ones that squish people?
Six months of hunting, six months of research and paying coin to scholars and sages, and now that we have the legendary wand of Geohadris the Stone King, it only summons stupid boulderkin? I am outraged beyond imagination!
Mapmaker's bane, a few of these can ruin a decade of cartography!
THE GNOMES OF UDNALOR: Part I
Upon entering the deep underrealm of Udnalor, one must first pass through the upper halls, which were the residences of the gnomes in days of past glories. Now they have abandoned the fading tapestries to the worms and moles, and an uncanny silence reigns, laid over the oaken tables like the thick layers of dust and humus.
There may be creatures which now inhabit these areas: nests livid with giant maggots, rats and other vermin.
The watchtowers and passageways which lead to the Overground are frequently trodden, however. After all it takes a great many small humanoids to hoist a single giant rabbit corpse back through the fathoms of earth.
The gnomes primarily hunt giant rabbits with bows and arrows tipped with the subterranean poisons concocted by their best alchemists.