2002 · ソースブック（プレイを拡張するルール／オプション）
Codex Mysterium (d20 3.0)
This d20 supplement expands magic and spellcasting for fantasy campaigns, with particular ties to the Sovereign Stone setting. It introduces rules for creating custom spells, casting spells from memory without restudying them, and combining the power of multiple wizards. The book includes more than two hundred spells for Elemental and Void mages, new prestige classes, and additional rules for spell creation. It also details the setting’s battle-mages, elven Wyred, mage guilds, Nimran priests, and dwarven Firemages, while remaining usable with other d20 System campaign settings.
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種族ベース（プレイヤーの種族/種がゲームプレイに影響する）ダイス（主にd20）ダイス（各種）
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。