Claw is an uninhabited tropical island on Serpent Isle.
In the First Age of Darkness, it was host to a dungeon called "The Dead Cat's Life II."
In Ultima VII Part Two, the normally inaccessible isle is only able to be explored by first using cheats to teleport there. Its shores, roamed by a small population of cats, are littered with human remains and the vestiges of a primitive settlement. Unique features can also be found in the form of large feline statues and wall carvings. These adorn the entrance to a cave, within which are duplicates of most of the game's major plot-related items, as well as a plethora of magic armour and weapons. A teleporter found outside another of the cave's entrances returns the party to Monitor, while a stairwell at the end of the tunnel through the island's lesser, southeastern mountain leads to the Dream Realm.
There are also some other seemingly unfinished caves and Ophidian ruins hidden beyond reach inside the greater mountain. These are remnants of the game's original plot design, which would have allowed for Claw to be visited as a legitimate location. For more information about the abandoned plans for Claw, see Cut Material in Serpent Isle.
Edit: Claw is in fact reachable through a legitimate method. On the isle of Moonshade, there is an abandoned house on the western side with several traps inside. If you stack the handily-provided boxes and walk onto the roof, there is a hidden teleporter behind the chimney that will take you to Claw. (much the same as the hidden teleporter to the cheat room found in Trinsic blacksmith shop in Black Gate).