The Lapsed Bear of Stormness was a Talking Bear of Narnia, which lived some time during and after the Golden Age.
Nothing much is known of the bear's past, but it had apparently reverted to wild bear habits, thus becoming dangerous. It lived somewhere on the Narnian side of Stormness.
The beast fought with Prince Corin, the Thunderfist of Archenland, sometime during the prince's adulthood. Corin had climbed up to the bear's lair one winter's day, when snow was on the hills, and fought it for thirty-three rounds without a timekeeper.
The bear apparently lost the fight, because by the end of the fight, it couldn't see out of its eyes, but as a result it "became a reformed character".