I think it takes place when silverstar (char in kit to leader) died of old age, but I don't think that's possible, because sparrowtail (older then silver) is still living according to west woods over borders.
btw the main char is called sliverstar not silver hehe and sliver ran away to the barn with nightmare (kinda visible in overborders) and this is after cryssies/crystal(forgor suffix) kits are warriors sooo kinda