Only tool with multi-layer caves
Underdark Map Maker
Build multi-layer cave systems for your D&D campaigns. Three Underdark depths with vertical connections, generated cave networks, and fog of war on every layer.
Free to try. Underdark layers included in the Game Master plan.
Try it — click the tabs or gold triangles to switch between depth layers.
Three Depth Layers
Caverns
The first layer below the surface. Fungal forests, dripping caves, flooded passages, and cavern networks where drow outposts and svirfneblin warrens hide. Most accessible to surface dwellers.
Deep Caverns
Deeper and more dangerous. Lava tubes, mineral deposits, geothermal vents, and chasms that split the earth. Home to ancient horrors and things that have never seen sunlight.
The Underdark
The deepest reaches. Lava lakes, crystal veins, stalagmite forests, and glowing grottoes where reality thins. End-game territory for the boldest parties.
Connect layers. Generate caves.
Link layers with stairs, shafts, tunnels, and magical portals — connections that let your party descend naturally through your world, and follow them in the shared view.
Generate the Underdark with the rest of your world: branching cave networks on up to three levels, underground lakes and rivers, and drow, duergar and svirfneblin holds named in their own tongues, each with a DM note on who lives there and how to get in. Every generated cave is fully editable — tweak anything by hand.
Each layer has independent fog of war. Reveal the Caverns without spoiling what's below. Dynamic vision adapts to terrain, weather, and time of day.
Layer reference ghosts another layer faintly beneath the one you're editing, so a cavern lines up perfectly with the river overhead and a dungeon level matches the floor above it. It shows only in the hexes you haven't painted yet, so your current layer stays clear — or hold Space to peek at the full layer beneath, then release to keep working.
21 Cave Terrain Types
Purpose-built for subterranean worlds, each with its own color and icon:
Start Building Your Underdark
No other hex map tool offers multi-layer cave systems. Try the editor free, then upgrade to unlock Underdark layers, fog of war, and underdark generation.
Frequently Asked Questions
Can I create Underdark maps online for free?
Yes — Hexer is free to start. The Underdark layer system is a Pro feature, but you can explore the editor and surface map tools for free before upgrading.
How many Underdark layers does Hexer support?
Hexer supports three subterranean depth layers — Caverns, Deep Caverns, and The Underdark (the Upperdark, Middledark, and Lowerdark of classic D&D lore) — plus the Surface. Each layer has its own hex grid, terrain, notes, fog of war, and connections to adjacent layers.
Can I connect Underdark layers to the surface?
Absolutely. You can place vertical connections like cave entrances, mine shafts, staircases, and portals between any adjacent layers. Players can navigate these connections in the shared live view.
Does fog of war work underground?
Yes. Each Underdark layer has independent fog of war. You can reveal hexes per-layer as your party explores, keeping undiscovered caverns hidden. Fog state is preserved between sessions.
Can I line up one layer with the one above it?
Yes. Layer reference (a Pro feature) ghosts another layer faintly beneath the one you're editing, so a cavern can line up with the river overhead or a dungeon level with the floor above. It shows only in the hexes you haven't painted yet, and you can hold Space to peek at the full layer beneath at any time.