Here is a cave generator I made, for use in your hexcrawl campaigns.
To generate a cave, first draw an entrance tunnel 30-60 ft in length. Then, roll a d20/d12/d10 for a large/medium/small cave system as well as a d6 and consult the following table. I recommend using 10sq/in graph paper for a large cave system.
There is also a sub-table for Chambers:
Click to enlarge.
I will explain things roughly in the order they appear, first for the main table and then for the chamber sub-table, unless I feel they are self-explanatory:
- Tunnels narrow on a roll of 1 on a d6 and widen on a roll of 6. In a normal cave tunnel, two man-sized beings can walk abreast and upright. After narrowing once, it may only be passed through one abreast. After narrowing again, man-sized creatures must crawl on their hands and knees. Armor and backpacks will make this more difficult. Narrowing a further time means that only a halfling-sized character wearing no armor or backpack can squeeze through on their belly, and must save vs. paralysis or become stuck (lethal).
- The d12 rolled to determine a curving passageway uses a "clock face" system. If the direction indicated by the d12 is back the way the party came, the passageway does a hairpin turn. If the direction indicated by the d12 is the way the party is currently going, the passageway does two tight hairpin turns to form an "S" and continues in the direction it was originally going.
- A gentle slope is a mere feature of the cave and will not bring characters to a new level, unless it continues for 120ft. or longer.
- For a chamber, roll the d20/d12/d10 twice to determine its width and height, taking note of how many exits there are (for example, rolls of 3 and 10 would mean a chamber 30ft by 40ft with two exits). Roll a d12 to place the exits around the chamber (which are generally round). If an exit should be placed where an exit already is, that exit is now hidden (e.g. it is a small crack in the wall that can be found and squeezed through, hidden behind a stalagmite, & c.)
- When stocking a chamber, "faction" indicates the monster or type of monster whose lair it is, if applicable. Otherwise, use the wandering monster table. Here is an example of a wandering monster table appropriate for caves:
- Beetle, Fire
- Green Slime
- Lizard, Gecko
- Shrew, Giant
- Snake, Cobra
- Spider, Crab