2003 · ソースブック（プレイを拡張するルール／オプション）
Monsters of the Endless Dark
This illustrated d20 monster manual presents dozens of subterranean creatures and the underground realms they inhabit. Each entry includes descriptions, artwork, and notations covering details such as diet, habitat, and sleeping habits. The collection is framed as a guide compiled from decades of exploration, providing material for adventures in unlit realms of earth and stone. An accompanying online resource offers community support and fan-submitted entries.
スキルベース（スキルを購入または獲得）属性／ステータス制（STR、CON、PERなど）レベル制（XPを獲得してレベルアップ）
ゲーム情報（人数、プレイ時間、対象年齢、クレジット）の出典：BoardGameGeek。