Encounter Crate: Dungeon Crawl

From the introduction:

Seith of Sundergall, the devourer of all things, has lived below the crust of the world in the deeps, in the caverns, in the dungeons. A gelatinous mass, older than reckoning and with an insatiable hunger for all things living and dead. It has devoured the earth and stone, carving its way across the deep places seeking its fill, but never finding satisfaction. What once was a simple gelatinous cube has become a terrible creature of legend within the deep places. Drow fear it, goblins worship it, and the world above knows nothing of it.