Sins of a Solar Empire II adds fourth faction Eidolon in $29.99 Harbinger expansion

Fans of Sins of a Solar Empire have waited two decades for this announcement: the franchise is getting its fourth playable race for the first time. The Harbinger expansion for Sins of a Solar Empire II launches on September 3, 2026, with the new Eidolon faction as its centerpiece.

In the lore, the Vasari have been fleeing the "great threat" that destroyed their empire for nearly 10,000 years. For 35 years, they warned anyone who would listen about its approach, and now that threat has finally materialized as the Eidolon. Unlike other races, the new faction does not fight over planets, trade routes, or wealth—its goal is to spread corruption and strike enemies with cloaked fleets.

The Eidolon mechanics revolve around corruption: the more planets and units it covers, the more power and advantages the faction gains. The Eidolon do not value typical assets like other races, but they exploit them to spread their corruption more effectively, transforming everything they encounter into tools for their own empowerment.

"Sins of a Solar Empire fans have been waiting for this reveal for a very long time," said Brian Clair, Director of Publishing at Stardock. "The team has been focused to make sure we don't disappoint and give players a new, unique experience."

The Harbinger expansion is now available to wishlist on Steam. It will also arrive via the Epic Games Store and the game's official website. The expansion carries a $29.99 price tag, while owners of the $99 premium edition or the Sins of a Solar Empire II: Content Pass for $59.99 will get it at no extra cost.

The release comes less than two years after Sins of a Solar Empire II itself hit shelves in August 2024. Since launch, the game has received several updates, but Harbinger marks the first major story-driven expansion to introduce a fully new faction.