The third Master Set in Heroscape's history was the smallest to date, with 10 figures and 50 terrain pieces, and marked the beginning of the Dungeons and Dragons era of the franchise. It features a band of heroes to replicate a D&D adventuring party, with a set of connected missions to form a 'Dungeon Crawl' to fight the young black dragon Othkurik, and also introduced new Dungeon and Shadow tiles.
Contents[]

The contents of Battle for the Underdark.
Figures:[]
Ana Karithon, Tandros Kreel, Erevan Sunshadow, Darrak Ambershard, Pelloth, Deepwyrm Drow, Feral Troll, Othkurik the Black Dragon
Terrain:[]
- 2 Dungeon Tiles (24 Hex)
- 3 Dungeon Tiles (7 Hex)
- 2 Dungeon Tiles (3 Hex)
- 2 Dungeon Tiles (2 Hex)
- 2 Dungeon Tiles (1 Hex)
- 3 Rock Tiles (7 Hex)
- 2 Rock Tiles (3 Hex)
- 1 Rock Tiles (2 Hex)
- 1 Rock Tiles (1 Hex)
- 3 Sand Tiles (7 Hex)
- 1 Sand Tile (2 Hex)
- 1 Sand Tile (1 Hex)
- 1 Grass Tile (3 Hex)
- 1 Grass Tile (2 Hex)
- 1 Grass Tile (1 Hex)
- 12 Water Tiles (1 Hex)
- 8 Shadow Tiles (1 Hex)
- 1 Rock Outcrop with Shadow Base (3 Hex)
- 3 Rock Outcrops with Shadow Bases (1 Hex)
The water tiles included in this set were the matte water tiles seen in Version 2 of Rise of the Valkyrie and Swarm of the Marro.
Treasure Glyphs:[]
Potion of Healing, Talisman of Defense, Heroic Rune, Brandar's Chest
Accessories:[]
- 23 Wound Markers
- 8 Order Markers (Purple)
- 8 Combat dice
- 1 20-side die
- 1 Uncommons Sticker Sheet
Battlefields and Scenarios:[]
Ancient Sanctum Room 1: The Lair[]
- Basic Game: Ambush
- Master Game: Dungeon Adventure 1 - Ancient Sanctum Room 1: The Lair
Ancient Sanctum Room 2: Drow Ambush[]
- Master Game: Dungeon Adventure 1 - Ancient Sanctum Room 2: Drow Ambush
Ancient Sanctum Room 3: The Portal[]
- Master Game: Dungeon Adventure 1 - Ancient Sanctum Room 3: The Portal
Ancient Sanctum Room 4: The Ancient Sanctum[]
- Master Game: Dungeon Adventure 1 - Ancient Sanctum Room 4: The Ancient Sanctum