These are catacombs of a petty dynasty of sorcerors who ruled part of the Barbaric Frontier few hundred years ago. Now forgotten the catacombs lies abandoned covered in dust. Apart from the tombs, adventurers'll find there a shrine dedicated to some old forgotten tentacled good, a death-shrine and a treasury, but what lies beneath? Who knows.
Zombies, mummies, liche, carrion crawlers, oozes, skeletons and maybe few dedicated cultists or cannibals scavenging on the remainings of those who once dared to trespass.
Acid pools, dart throwers, spikes, falling roofs, curse glyphs, summoning glyphs etc.