2021 · ソースブック（プレイを拡張するルール／オプション）
Under Alien Skies
This sourcebook expands the Trinity Continuum: Aeon setting with information about the Chromatics, Coalition, and Listeners, including their societies and rules for creating characters from these species. It also introduces six additional alien species, including extinct or nearly extinct peoples and the malevolent Doyen. Storyguides receive advice for incorporating aliens into campaigns as encounters, allies, or protagonists, along with instructions for creating new species. The book also details alien technologies, from common devices to mysterious artifacts that remain poorly understood by human researchers.
スキルベース（スキルを購入または獲得）ポイント制（ポイントを割り振ってスキルや能力を得る）属性／ステータス制（STR、CON、PERなど）
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。