Sand-choked shrines to ancient gods, abandoned abbeys, and cultists’ crypts are built as places of worship and havens for the faithful, but are also designed to guard against profane intruders. A temple usually contains barracks, living areas, and well-defended sacred spaces.

Tiers. Temples range from catacombs at tier 0 to vast, underground cathedrals at higher tiers, with tiers 0 to 2 being the most common.

The typical sewers beneath fantasy cities are magnificent public works from a bygone age. A mishmash of deserted concourses, covered riverways, claustrophobic tunnels, and buried ruins, they are a royal road for thieves, monsters, and adventurers alike.

Tiers. Sewers are rarely tier 3 or 4. Below the sewers, deeper and more dangerous areas are usually ruins, tombs, or other locations.

A weathered castle, a haunted palace, an abandoned labyrinth—any of these constructions may fall into ruin. A ruin is distinct from other dungeons in that it no longer serves a particular purpose. It may be inhabited piecemeal by different groups, but no one ruler or gang controls more than a fraction of it .

Tiers. Ruins can be any tier, with older and more remote ruins tending to house stronger monsters.

Almost every sapient species digs something they want out of the earth. Dwarves dig for adamantine, shadow elves for mithral and dark iron, grimlocks for copper, and everyone mines for iron, gold, salt, and precious stones. When metal and ore are abundant, mines are busy places, but once the supply of that material dwindles, they become eerie, crumbling labyrinths in the lightless depths of the world.

Great war mage colleges, secluded wizard’s towers, and alchemists’ workrooms are all examples of laboratories. Laboratories are places of research and typically include unique magical and alchemical effects that can’t be found anywhere else. In addition to living spaces, a laboratory requires workrooms and libraries.

Tiers. While laboratory inhabitants often include students and apprentices, the masters of large laboratories are commonly tier 3 or 4.

Under the earth lie twisting passages, vast caverns, and underground rivers, all cloaked in endless darkness. The environment itself can be just as dangerous as its inhabitants.

This generator lets you map a cave system. For Underland travel, see Underland Realm in Trials & Treasures.

Tiers. Tier 0 and 1 adventurers measure themselves against natural caves and caverns. Tier 2 and 3 adventurers delve deeper, into Underland itself.

Underland boasts many of the same vehicles that ply surface roads and seas. Shadow elf couriers use giant spider-drawn chariots, and galleys sail the Midnight Sea. Safe from inclement weather, airships fly through mammoth caverns and miles-long ravines.

A few vehicles are unique to the Underland. Aboleth-built submarines ferry treasure and thralls to underwater cities. Armed with torpedoes, aboleth submarines fight a never ending war against the fleets of sunless mariners.

Table: Underwater Vehicles