The Hand of Vecna

The Hand of Vecna can be obtained by killing Vecna in the Chaotic Quest, provided you don't not digest or disintegrate him. It is one of the most powerful Artifacts in SLASH'EM. Although it is guarded by an army of L, Z, V and Vecna himself, most adventurers go through the trouble of killing them to aquire it. If you eat the hand, you will get 150-199 damage, so this is a Bad idea.

Invoking
If your Luck is lower than -9 you get the following message: and recieve 5-24 damage. Otherwise, and you summon 4-7 tame graveyard creatures. You also take a -3 penalty to Luck and alignment.
 * "The Hand claws you with its icy nails!"
 * "Creatures from the grave surround you!"

In Dungeons & Dragons
In the Greyhawk setting, the hand was one of the two things which remained after Vecna fought Kas the Bloody-Handed (the other thing was the eye).