The Beast is a boss found in Upper Blackrock Spire. It appears to be a Core Hound that has been captured by the forces of Nefarian for use in his breeding experiments. (Experiments on other core hounds could account for the creation of Chromaggus, a core hound-like dragonkin who is the penultimate boss found in Blackwing Lair.)
At some point before he is encountered by a party, the Beast had swallowed Finkle Einhorn, a gnomish adventurer who has survived in the Beast's stomach for an unspecified period of time. Skinning The Beast will free Finkle.
Essentially, a tank will need to keep aggro on The Beast at all times as he hits extremely hard and can kill a cloth wearer in 2 or 3 hits. The rest of the raid will want to DPS him. As long as the Main Tank can keep aggro (best to say the Main Tanks, since it is unlikely that aggro can be consistently held, due to The Beast's oft-cast fears and random charges) and you have sufficient healing, this fight should be a simple one. He may drop , which increases skinning by 10, so anyone in the group with a skinning skill of 300 should roll on this if they don't have it already, otherwise it can be greeded. It is vital to have a player in the raid who can skin The Beast, as they can receive the and also reveal Finkle Einhorn, who is the start of a quest chain.
NOTE: With the release of the Burning Crusade,Wrath of the Lich King and Cataclysm, it is possible to raise your profession level to a maximum of 525, thus making it a simple task for any skinner who has been to at least Outland to skin The Beast.