2004 · ソースブック（プレイを拡張するルール／オプション）
Beyond the Horizon
Heroes brave the unexplored regions of Gamma World, encountering new races, monsters, and mysteries as they cross its changing lands and seas. Their expeditions bring knowledge and power to their tribes. This sourcebook explores how people and civilizations differ across continents and reveals secrets hidden in unexpected places. It also provides information about Gamma World, along with rules and guidance for creating new details and adventures.
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。