Sheathclaws is a planet colonized by humans aboard Angel's Pencil (plus Selena Guthlac) and a rogue Kzin telepath called Shadow with a harem of six kzinretti. It orbits a star 98 light years from Earth, and kept its existence secret for several centuries. While the exact location is unknown the planet is known to lie beyond Kzinti Patriarchy space.
After being settled the planet kept its isolation for the next three hundred years, contacting no other sapient species and being unable to send messages to Sol system due to any message having to pass through Kzin space. At some point prior to 2658 news of hyperspace travel arrived in the planet allowing its inhabitants to venture out for the first time in centuries.
Kzinti from Sheathclaws differ in a number of ways from the Patriarchy's Kzinti. They are much friendlier with humans, and seem to have adopted human customs such as a taste for human food, and the speaking of Interworld as their first language instead of the Hero's Tongue. Likewise being descended from the telepath Shadow makes all of them potential telepaths, a fact that makes the Kzinti Patriarchy very interested in finding the location of the planet. Kzinti in Sheathclaws also practice a form of wrestling where the claws are capped with button-like corks. 
Locations in the planet include Blood Park, Touchdown and Offcentral Park. The planet is said to have chains of lakes running from mountain to the sea.
- Official Timeline at Larryniven.net