The Flinty Ridge
by WingofCootThe Flinty Ridge is named for its large outcrops of flint and especially chert, sitting among even more extensive limestone. These higher hills are sharply distinct from the predominant sandstone and shale making up the rest of the Sylvan Highlands' elevations. The porous limestone causes rainfall to drain away quickly, contributing to the relative lack of tree cover here (very unlike the rest of the Sylvan Highlands).
The limestone in the Flinty Ridge contains a large number of caves; most of these are isolated, but a few connect to extensive cave systems. The isolated caves are often lairs for Cave Bears or groups of Rock Baboons. The deeper reaches of the extensive cave systems contain a variety of deep underground life-forms, including the typical fungi, oozes, and other 'dungeon lowlife' (Shrieker, Yellow Mold, Gray Ooze, Ochre Jelly, etc.), but these never venture near the surface or the perpetual light of the inner sun.
At least one of these cave systems extends beyond the Flinty Ridge, connecting to underlying cave systems beneath the mountain spine of southern Jomphur - and perhaps a greater system underlying the Hollow World itself?