Overview
The Underdark is the vast tunnel network beneath Terra, carved by millennia of volcanic activity under Titania. It connects the surface cities to the subterranean dwarf-and-drow city of Niflheim, to the Buried City and its Sarcophagus facility, and to the deeper drow territories beyond. It is home to myoconids, flumphs, basilisks, shadows, and more dangerous things — and the Al’ar family has been mapping it extensively, for reasons they have not made public.
Each layer descended represents a different era of Titania’s volcanic past, now colonised by life and carved through by the old civilisation’s tunnels.
Regions
Layer 1 — Old Volcanic Tunnels
The uppermost tunnels: cooled lava tubes with mineral-striated walls, used by the old civilisation’s workers and later by early Underdark pioneers. Calm mushroom forests and caves occupy the larger chambers, lit only by bioluminescence.
Notable sites:
- Myoconid Village — will shelter non-threatening travellers; a place of quiet diplomacy.
- Settlement Remains — collapsed ruins of early Underdark pioneers who didn’t last long down here.
- Wandering flumphs, who colour themselves by mood — blue for peace, red for danger nearby.
Layer 2
The mushroom caves deepen and take on a purple-blue hue. Flooded grottoes and minor crystal caverns appear, the latter home to trolls, basilisks, spiders, and shadows. Older, wider volcanic tunnels here show tool marks and deliberate carving by the old civilisation.
Notable sites:
- Myoconid Colony — larger and more established than the village above; may know more of what lies further down.
Layer 3 — The Crystal Layer
Originium is most abundant here, growing through crystal caverns, old magma chambers, and grottoes, integrating into the geology itself. The old civilisation’s reinforced tunnels — archways, carved passages, sealed chambers — connect their installations to one another through this layer.
Notable sites:
- The Buried City — the largest known ruin of the old civilisation, sealed beneath crystal and cooled magma. Its Sarcophagus sits on the city’s western edge, connected to an old reactor-plant to the south.
- Niflheim — the dwarf-and-drow city roughly one kilometre below Titania’s foot, likely situated somewhere around this depth, though it has not been placed on any layer map yet. Its climate cycles between warmth and deep cold with the western underwater volcano’s activity.
Layer 4 — The Deep Layer
The deepest layer yet explored.
Notable sites:
- The Chaos Caverns — a vast, disorienting network of tunnels, shafts, and floating stone islands over abyssal drops. Passages shift and mapping seems to resist itself here, whether from residual magic, unstable geology, or something else. The strangest and least understood environment in the Underdark.
- None further yet documented.
Notes
- No single map currently unifies the four layers with Niflheim’s depth or the Buried City’s position — their relative placement is approximate, drawn from DM discussion rather than a finalized layer map.
- The Al’ar family’s motive for mapping the Underdark so extensively is deliberately withheld.
- A mind flayer is reported active somewhere in the deeper tunnels by local myoconids and flumphs