The Nightsaber Cub is a new virtual vanity pet now available in World of Warcraft: Cataclysm PTR 4.1. You can go to Lando Longshot in Booty Bay to redeem the pet now that you can and while it lasts.

The Nightsaber Cub will be a loot card from the World of Warcraft TCG: Twilight of the Dragons expansion pack (release date still to be determined).