The Wormholes
Deep beneath the surface of many of the planes winds a network of tunnels and caverns. Somewhat analogous to the Underdark of the Prime—and indeed, the two networks do occasionally overlap—the Wormholes are a vast sprawling mass of passages branching out from Pandemonium where the exiles live, and tracing currents of secrecy, scurrilousness and underhanded double-dealing right across the Lower Planes. The Abyss, Carceri, the Gray Wastes, Gehenna, Baator and Acheron are all said to have connections to the Wormholes, and the tunnels dig into the Outlands as well. Rather more worrying, perhaps, are the tales of secret passages that snake and sneak all the way to the Upper Planes, emerging on windswept Bytopian mountainsides, the crystalline caverns of Mount Celestia and deep wooded groves of Arborea. If locals of these planes find a connection to the Wormholes, woe betide anyone beneath the surface, because like as not the tunnel will be forcibly collapsed at the first opportunity.
Used by smugglers, bandits, fiends, assassins and knights of the cross trade alike (mainly to slip things that they shouldn’t to the Upper Planes), the most dangerous feature of the Wormholes are the other travellers you might meet, who’re more likely to slice your throat than stop to greet you. Should you be fortunate enough to avoid their nefarious advances, you ought to keep watch on the passage roof, not just for lurkers above, but also rockfalls and cave-ins. The chant goes that the Wormholes are passages left behind by giant planeshifting worms who tunnel between planes in search of food. Whether food includes humanoids is unclear, but nobody’s ever seen one of the creatures, so it could be that they’re long-dead. That wouldn’t explain why new tunnels appear all the time to replace ones that’ve collapsed though.
Source: Jon Winter-Holt, mimir.net
