2018 · ソースブック（プレイを拡張するルール／オプション）
Border Elemental Planes
This supplement explores the Border Elemental Planes of Ash, Ice, Magma, and Ooze, with guidance on reaching, surviving, and traveling through each realm. It details powerful entities, dangerous environmental hazards, notable sites, treasures, adventure hooks for all tiers of play, and random encounter tables. The book adds 13 monsters, including border elementals, a frost salamander, lava shark, mud serpent, ragewraith, and several creatures and swarms. It also introduces three player options: the Oath of Clarity for paladins, the Ooze Magic origin for sorcerers, and the River of Rage patron for warlocks.
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）ダイス（主にd20）
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。