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Spoiler warning: This page contains considerable plot spoilers for almost the entire back half of the Rio Narro story arc in 🟩 RSR - Bloodtiger.
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Reader reference: Caisteal is a key Sun Jin colony world in the Bethany system—home of the Caistealian people and a major setting for multiple rev2.5 events.
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Caisteal is the closest habitable world to Bethany, sharing the same solar system and serving as an important colony world for the Sun Jin Empire. It’s widely described as a “green-and-snow world”: broad green regions and forested terrain broken up by heavy snowfields and long cold seasons. In rev2.5 (Rio’s POV), Caisteal is also the homeworld of the Caistealian people, including notable figures like Rio Narro.
The planet matters to the story largely because it is where the Sun Jin’s living-weapon program intersects with Forza’s escape arc. Caisteal is the setting for Sun Jin weapon testing conducted against a drugged and controlled prisoner—Forza Ninetails—and it becomes the backdrop for the chain of fallout that follows Rio’s storyline.
General
Click other tab to read details of the following events: RD10-003 Incident Battle at Birch
Spoilers
RD10-003 (R&D10-003) is a Sun Jin weapons-research black site on/associated with Caisteal: a controlled facility built to hold, condition, and repeatedly test Forza Ninetails as a living weapon. In practice, it’s less a conventional “base” and more a machine for turning captivity into results—sedation, containment, trials, evaluation—designed around prototype close-quarters systems and armor integration such as the Gotanenks Armor in attempts to make the system mass producible. The project is closely tied to Professor Denim, whose authority becomes a critical point of failure when the facility is compromised.
RD10-003, a Sun Jin Imperial weapons research and development black site.
The RD10-003 Incident is the moment Rio’s mission turns personal—and violent. While investigating the facility, Rio Narro reviews Professor Denim’s recorded results and sees what the program is forcing Forza Ninetails to do against his will, including slaughter that implicates Caistealian victims. Disgusted, Rio kills Denim and the researchers present, then destroys the containment vessel Forza is housed in while he is still sedated—compromising RD10-003 from the inside.
When alarms escalate and Forza reclaims his weapons and armor to begin his own escape, Rio intervenes again: she makes a precise rifle shot to his helmet that knocks him unconscious and sends him down a ravine, deliberately separating him from the search grid. Using her authority as a special agent, Rio orders the soldiers to remain on-site while she “retrieves” him—then instead nurses him back toward stability as she guides him toward Birch in search of a way off-world, setting up the events of the Battle at Birch.
The Battle at Birch is the rural set-piece that follows Rio and Forza. Rio and Forza attempt to disappear into the farming village of Birch on Caisteal, but a Sun Jin recovery force comes in to reclaim Forza and erase resistance. The fight culminates with Flarion entering the engagement and removing Forza from the battlefield—an intervention that ends the recovery attempt but leaves Rio behind to deal with the aftermath, and pushes the story into its next phase.
