Terrain Trays are part of the Dungeon of Doom series. With the exception of the overlay grid, they are made of metal with a fabric cover with different terrain features on each side. The overlay grid is a flexible clear plastic mat for the terrain trays. These items were initially available as an add-on packs during the Dungeon of Doom Kickstarter. On one side, the terrain tray depicts a stone surface, and on the other, it depicts either a lava, water, or acid surface. Terrain Trays come in two sizes: 12x12 and 8x4 12x12 Terrain Tray Mats are sold individually and in Terrain Tray Packs Terrain Tray Packs comes with 4 pieces:(2) 12x12 Mats and (2) 8x4 Mats 8x4 Mats Terrain Tray Packs come with (3) 8x4 Mats Gaskets for the Dwarven Forge terrian tiles and magnets to fit in the gaskets were accessories available to modify the Dwarven Forge tiles so they would remain fixed to the metal terrain trays.