Node Mapping the Underdark

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The GM map is just a node map showing each site/intersection as a node with the paths leading away from it connected visually in their respective position on the compass rose (i.e. North = up, South = down).

If at any point when mapping an area, if there are at least 6 passages unexplored, the next area will be a dead end on a d6 roll of 6+. (DM may modify this by up to +3 depending on circumstances)

Unless otherwise specified by the location or site, for each node, roll 2d4 to get the number of passages that connect to the node. If node is a settlement with unspecific exits, add 2 to this roll with a max of 8 exits. Each node is one of the locations on the map. For each passage that connects to a node, roll 1d8 to determine the cardinal direction the passage enters/exits the node from with North = 1, NE = 2, etc. Start with which the route the party enters the node.

In general, it is best to have at least two nodes between Sites/settlements. If a Site/Settlement option is rolled, instead have a ruin or creature lair (whichever is more appropriate given surroundings) and the next appropriate node is automatically a Site/Settlement. First Cavern counts as a settlement for this purpose.

Endless Caverns

Endless Cavern nodes are anywhere from 400 yards to a mile on a side while the passages are, on average, about 75 yards wide and generally no more than 200 yards wide at any given point.
When a passage is taken for the first time, roll 1d4+1d6-2, minimum 1 (1-8 with the probablity being highest of 3-5 – source: to determine the distance in miles to the next node.

Endless Cavern Nodes
Roll Result
1 just an intersection, roll an extra encounter check
2 just an intersection, nothing else of note
3 intersection with a creature lair, roll on Creature Chart to determine type
4 new Site or Settlement, roll on Sites & Settlements Chart
5 new Location, roll on Location Connections Chart
6 previously discovered Endless Caverns node; determine randomly

The Labyrinth

Each labyrinth node is an area 100-200 yards on a side. The passages are about 15 yards wide.

After rolling for connecting nodes, roll 1d8 for each and on a 3+, the node continues in that direction rather than just being a passage – treat the new node as any other as far as determining passages/node continuation. (max 2 new extensions per node. I.E. node A rolls 2 3+ to extend into Nodes B and C, node C rolls 3 3+s but can only extend 2 times into nodes D & E where we would roll again and node B rolls 1 3+ so it expands into node F and rolls again)

When a passage is taken for the first time, roll 1d4+1d6-2, minimum 1 to determine the distance in tens of yards to the next node. Any time a passage goes in the direction of a known node that has no exit in that direction, the passage is a raised passage over the old.

The Labyrinth Nodes
Roll Result
1 mushroom patch
2 fungal grove
3 rock grove
4 as 1, 2, or 3 with a creature’s lair; roll on Creature chart to determine what
5 new Site or Settlement; roll on Sites & Settlements chart
6 new Location; roll on Location Connections chart

Random Encounters when travelling

See the chart below to determine how many Encounter Checks to roll between nodes. For each check , roll a 1d6 and on a 6+, an encounter happens (at the DM’s prerogative there may be an addition to the roll of up to +3 based on circumstances). Then roll on Encounter Chart to see what is encountered

Checks between nodes
Area # checks
Endless Caverns 3
Labyrinth 1
Great Undersea 2
Grand Chasm 1
Glittering Caves 1
Fungal Fields 1
Freshflow River 1
Random Encounter
Roll Encounter
1-2 spoor/sign – roll d6: 1-2 random civ, 3-6 wild creatures
3 patrol of random civilization roll on Random CIv chart
4-5 wild monster(s) roll on wild creature chart
6 Resource cache (such as a vein of ore or abandoned cart of cloth)
Random Civ Encounter
Roll Endless Caverns Labyrinth Fungal Fields Glittering Caves Grand Chasm Great Undersea Freshflow River
1 cthaka goblins cthaka goblins Goska goblins Lagdush orcs ushad kobolds cthaka goblins Muzga Lizardfolk
2 goska goblins Shakil Lizardfolk anvilhold dwarves rakand ogres anvilhold dwarves
hagga goblins Gorlutz orcs lagdush orcs
kordaku jinnai
akkad kobolds
Chapel Black Friars gurak muzga swamp creatures
Clockwork Tower Hermit
Fungal Field grand chasm glittering caves fungal fields great undersea freshflow river great undersea
Glittering Cave endless caverns endless caverns endless caverns endless caverns grand chasm
Labyrinth fungal fields labyrinth labyrinth
Grand Chasm
Roll Creature Roll Creature
Drake Shocker Lizard
Bear Cat
Grick Ankheg
Giant Slug Otyugh
Fungus Walker Undead
Spider Worm
Sites & Settlements
Endless Caverns Labyrinth Glittering Caves Fungal Fields Freshflow River Grand Chasm
ruin Pillar of the Black Friars First Landing Mineshaft Goska Muzga Island Ushad
The Clockwork Tower Islington’s Lair Anvilhold Mineshaft Shakil Anvilhold Landing Rakand
The Chapel of All Deities roll 1d10, on 10 – find Hermit’s Hut Lagdush Gorlutz Lagdush Docks Gurak’s Lair
Cthaka Cthaka
Anvil Gate
Location Connections
The Winding Stair (Grand Chasm) Grand Chasm Endless Caverns (multiple) Glittering Caves Freshflow River Delta (Great Undersea) The Winding Stairs (Endless Caverns)
Grand Chasm Midway Endless Caverns (multiple) Fungal Fields Endless Caverns Midpoint Cave (Endless Caverns)
Labyrinth (multiple) Fungal Fields Labyrinth Labyrinth Entrance
Glittering Cave (multiple) Undersea Shore
Fungal Fields
Resource Cache
Roll Resource
1 water source
2 ore vein
3 Food source
4 abandoned cart of (insert resource)
5 Dead bodies of (insert two civ/creatures) around pile of (insert resource)

Node Mapping the Underdark

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