Source: Dungeon Master's Guide

Wondrous item, artifact (requires attunement)

Seldom is the name of Vecna spoken except in a hushed voice. Vecna was, in his time, one of the mightiest of all wizards. Through dark magic and conquest, he forged a terrible empire. For all his power, Vecna couldn't escape his own mortality. He began to fear death and take steps to prevent his end from ever coming about.

Orcus, the demon prince of undeath, taught Vecna a ritual that would allow him to live on as a lich. Beyond death, he became the greatest of all liches. Even though his body gradually withered and decayed, Vecna continued to expand his evil dominion. So formidable and hideous was his temper that his subjects feared to speak his name. He was the Whispered One, the Master of the Spider Throne, the Undying King, and the Lord of the Rotted Tower.

Some say that Vecna's lieutenant Kas coveted the Spider Throne for himself, or that the sword his lord made for him seduced him into rebellion. Whatever the reason, Kas brought the Undying King's rule to an end in a terrible battle that left Vecna's tower a heap of ash. Of Vecna, all that remained were one hand and one eye, grisly artifacts that still seek to work the Whispered One's will in the world.

The Eye of Vecna and the Hand of Vecna might be found together or separately. The eye looks like a bloodshot organ torn free from the socket. The hand is a mummified and shriveled left extremity.

To attune to the eye, you must gouge out your own eye and press the artifact into the empty socket. The eye grafts itself to your head and remains there until you die. Once in place, the eye transforms into a golden eye with a slit for a pupil, much like that of a cat. If the eye is ever removed, you die.

To attune to the hand, you must lop off your left hand at the wrist and the press the artifact against the stump. The hand grafts itself to your arm and becomes a functioning appendage. If the hand is ever removed, you die.

Random Properties. The Eye of Vecna and the Hand of Vecna each have the following random properties:

Properties of the Eye. Your alignment changes to neutral evil, and you gain the following benefits:

Properties of the Hand. Your alignment changes to neutral evil, and you gain the following benefits:

Properties of the Eye and Hand. If you are attuned to both the hand and eye, you gain the following additional benefits:

Destroying the Eye and Hand. If the Eye of Vecna and the Hand of Vecna are both attached to the same creature, and that creature is slain by the Sword of Kas, both the eye and the hand burst into flame, turn to ash, and are destroyed forever. Any other attempt to destroy the eye or hand seems to work, but the artifact reappears in one of Vecna's many hidden vaults, where it waits to be rediscovered.