The Ryekin-class combat submarine was a type of small submarine used by the Srav Federation during the Cruentusian War, in response to the recognised need for Srav aquatic units. Small, and therefore difficult to detect by conventional scanners, the Ryekin was equipped with nuclear-tipped torpedoes and was powered by a small nuclear reactor, which meant that geiger-equipped sensors could easily sense it. It was also equipped with three ballistic misiles which it could fire on any land target, which meant that its presence struck fear into enemies. Nonetheless, it was very vulnerable to depth charges and mines.