How to Assemble the Modular Wall of Doom: Step-by-Step Terrain Setup

Quick answer

Assemble your modular wall of doom by building from the floor up: lay a stable base of floor tiles, lock wall sections together in short runs, and use corner pieces to turn the line. Anchor magnets and a flat, level surface do most of the work. Build in 2- to 3-foot sections, test the fit before adding height, and keep the wall low enough that players can still reach the table.

A modular wall of doom is only as good as its foundation. Whether you are walling off a ritual chamber or funneling players into a corridor, the wall needs to stay standing when dice hit the table and hands reach across the map. The good news is that a modular wall of doom setup is less about glue and more about order of operations.

This guide walks through the build in the order that prevents the usual problems: wobble, gaps, and walls that collapse the moment someone bumps the table. You will use floor pieces as a base, stack wall sections in manageable runs, and finish with corners and clamps. The same process works for caverns, dungeons, and city interiors, so you can reuse it every session.

Plan the footprint before you place a single wall

Sketch the wall line on paper or dry-erase mat first. Mark where doors, corners, and choke points go, then count how many floor tiles you need underneath. A wall of doom that sits on a solid floor base is dramatically more stable than one standing on bare table. If your layout is mostly walls with little floor, consider adding a few 1x2 Cavern Floor pieces under the corners to give the structure something to grip.

Decide how tall the wall should be. Two levels of wall sections read as a barrier; three levels can block line of sight completely but also block player reach. For most encounters, two levels plus a corner cap is the sweet spot. Write the height on your sketch so you do not improvise mid-build.

• Checkpoint: your sketch should show every corner and door before you open any storage bins.

Lay the floor base and check for level

Place your floor tiles first, pressing them together so the seams are tight. Run your hand across the surface to feel for high spots or gaps. A single raised tile will telegraph up through the wall and make the top sections lean. If a tile rocks, swap it for another or shim it with a thin piece of card under the table mat.

This is also the moment to confirm table coverage. Walls need floor to stand on, and a wall of doom that eats your entire play area leaves no room for miniatures. Leave at least two inches of open floor on the side where combat will happen.

• Common mistake: building the wall first and sliding floors underneath later. Always floor first.

Build the wall in short runs, not one long line

Start at one end and assemble 3 to 5 wall sections as a single run, then set that run on the floor base. Short runs are easier to align and less likely to bow. Connect each run to the previous one before adding height, and press down firmly so anchor magnets engage if your pieces have them.

If you are using pieces from the Underdoom line, the Yellow Fungus Corner (Corner B) is designed as a corner wall piece with anchor magnets, so it can act as a natural stopping point for a run. That gives you a clean joint instead of a long, flexible wall that wobbles in the middle.

• Checkpoint: press each seam and listen for the magnet click. If it does not click, reseat the piece.

Turn corners with dedicated corner pieces

Corners are where most walls fail. Do not force two straight sections into a 90-degree turn; use a corner piece so the load transfers down rather than sideways. The Yellow Fungus Corner (Corner B) from the Underdoom line is built as a corner wall piece and fits cavern-themed builds, which makes it a practical choice when your wall of doom runs through natural rock rather than cut stone.

Set the corner first, then build outward in both directions. This keeps the corner square and prevents the wall from drifting out of alignment as you add sections. If the corner sits slightly proud of the straight runs, check that the floor beneath it is flat before adjusting anything else.

• Common mistake: bending straight walls around a corner. It stresses the joints and causes gaps at the top.

Add height in one direction only

Once the base run is stable, add the second level. Work from one end to the other rather than stacking randomly, so each new piece sits on a settled section. Do not add a third level until the second is fully connected and pressed down. Height magnifies any lean, so a wall that looks fine at one level can look crooked at two.

If your wall needs to block line of sight for ranged encounters, a third level helps, but keep a gap or a doorway so players can still interact with the space. A solid wall of doom with no opening turns a fight into a stalemate.

• Checkpoint: sight down the wall from one end. If you can see a curve, fix it before adding more height.

Finish with dressing and a stability check

Dressing sells the wall and hides small gaps. Curtains & Rugs Dressing (Unpainted) can be dropped into indoor environments, and the freestanding curtains can block line of sight or act as alternate doorways. That gives you a soft vertical element that does not add weight to the wall itself. Rugs can also hide trapdoors or other features for players to find.

Before you start play, do a bump test. Nudge the table gently and watch the top of the wall. If it sways, add a corner brace or shorten the longest run. A wall of doom that survives a bump test will survive a session.

• Common mistake: skipping the bump test. Two minutes of checking saves a mid-combat collapse.

Wall of Doom Assembly Steps

1. Sketch the wall line and count floors: Draw every corner, door, and choke point before touching terrain. Count the floor tiles needed under the wall. Checkpoint: no wall piece goes down until the footprint is decided.
2. Lay and level the floor base: Press floor tiles tight, feel for high spots, and swap any tile that rocks. Leave open floor for miniatures. Common mistake: building walls first and sliding floors under later.
3. Assemble short wall runs: Build 3 to 5 sections as a run, then set it on the floor. Press seams so anchor magnets engage. Checkpoint: listen for the magnet click at every joint.
4. Set corners with corner pieces: Place dedicated corner pieces first, then build outward in both directions to keep the turn square. Common mistake: forcing straight walls around a 90-degree turn.
5. Add height from one end to the other: Stack the second level in order, then the third only if needed. Sight down the wall for curves. Checkpoint: fix any lean before adding more height.
6. Dress the wall and bump test: Add curtains or rugs for line of sight and hidden details, then nudge the table and watch the top of the wall. If it sways, shorten the longest run or add a corner brace.

Pieces that make the build easier

• Yellow Fungus Corner (Corner B)- Underdoom (Painted): Painted individual piece from the Underdoom line, designed as a corner wall piece with anchor magnets and suited to caverns and walls terrain setups. Use it as a stable corner anchor so your wall of doom turns cleanly instead of bending straight sections.
• 1x2 Cavern Floor - Underdoom (Painted): Painted individual cavern floor piece with a 1x2 footprint, made of Dwarvenite, includes anchor magnets, and is part of the Caverns Deep (KS6) expansion. These small floors give you a level base under corners and doorways without covering your whole table.
• Curtains & Rugs Dressing (Unpainted): A collection of curtain and rug dressing that can be dropped into any indoor environment; freestanding curtains can block line of sight or act as alternate doorways, and rugs can hide trapdoors or other features. Adds line-of-sight blocking and hidden details to a finished wall without adding weight to the structure.

A modular wall of doom setup rewards patience more than pieces. Floor first, short runs, dedicated corners, and a final bump test will keep your dungeon wall assembly standing through the whole session. Build it once this way and you can reuse the same process for every encounter.