Approximately 70% of TTRPG adventures take place in caves.¹ Because of this, it’s good to have some cave-specific TTRPG scatter terrain ready to hit the table! This build is extremely simple and a great way to use any larger pieces of scrap XPS foam.
What you’ll need
- XPS foam
- Toothpicks
- Wooden Skewers
- Dowels in assorted sizes
- Hot glue and hot glue gun (optional)
- Utility knife
- Mod podge glue
- Acrylic paint (dollar stores fine!)
Make the Rocks
Use a utility knife or proxxon cutter to slice your foam into some rock-like shapes. I recommend creating a variety of sizes and adding some curves to represent cave edges. Add texture with the utility knife and by pressing balled up tin foil into the foam. If you want to add some dynamic heights to your build, hot glue smaller platforms on top of larger ones to create more varied shapes. You should end up with something like this:

Get to the Point
Using your utility knife, sharpen the ends of your dowels. Snap or cut pieces to get a variety of lengths as desired. Press the unpointed end of your spears into the foam, keeping the shafts as vertical as you can. Natural stalagmites/stalactites are formed by gravity, so they are perfectly vertical – the straighter you are able to keep your points, the more authentic it will look.
Start with your thickest spears, adding one or two to your foam bases. You may want to press foam to the top of the spears too, to create a cave ceiling effect. Mix the heights of your spears to create a random, organic look.
Once you are satisfied with your thickest stalagmites, add in your thinner sticks, skewers, and toothpicks, working from largest to smallest. If you are unsure of placement, search for inspiration in images of natural forming stalagmites/stalactites.

Mod Podge
Some of your spears may not want to stay put. You can add a little glue to these as you go. To really cement your piece together, however, paint on a layer of mod podge mixed with black paint. This sticks everything in place while acting as a handy base layer. Be gentle when painting your spears – they are easy to knock of center!

Paint!
Using acrylic paint, paint your scatter terrain to match your dungeon tiles, or the general setting. Start with a dark base colour and allow it to dry completely. Once dry, dry brush over your terrain with a lighter accent colour.
The pallet I used in this project was simple: a heavy dry brush of red (covering most, but not all, of the black under layer), and a dry brush of pumpkin orange.
If you’re looking for other paint ideas, you can make a classic stone look with a very dark grey base, and dry brushing on lighter greys, brown/green (if it’s a dirty/mossy cave), and ending in a very light dry brush of white. Alternatively, I’ve always enjoyed a dark blue base with light blue/white dry brushing for fae or otherworldly environments. Follow your heart!

That’s it! You have your own cave scatter terrain. Happy crafting!
¹Source: Me, just now.