From publisher blurb:
A Mini-Dungeon adventure for 4 level 11 PCs
A powerful planar entity has drafted the PCs to test out alternate versions of cosmology, hoping mortal creativity might accomplish what immortal acumen could not. To succeed in their task the PCs must use this engine of creation to generate a miniature world, then defend that world from a miniature apocalypse.
The World Forge in Your Campaign
Sometimes, heroes must leave the comfortable confines of the dungeon for grander adventures. Rather than saving villages and kingdoms, such powerful PCs must now concern themselves with saving the cosmos. This adventure is a stepping stone between these two power levels, introducing PCs into the larger conflicts of the planes. The entity who created this bizarre engine might be divine, demonic, or utterly alien in nature depending on the needs of your campaign. However, its need for a “replacement world” offers foreshadowing for your choice of apocalyptic threats.