There are many powerful villains in the history of Dungeons & Dragons, but there are few as feared or admired as the arch-lich Vecna, who is one of the few D&D characters to ever ascend to godhood. Vecna has been the villain of several popular adventures, including Vecna Lives!, where he was indirectly responsible for killing several of D&D's most powerful wizards in a few rounds of combat. The D&D 5e Player's Handbook lists Vecna in the "Gods of the Multiverse" section, as he's the god of secrets in Oerth, but he has a history that predates his ascension.
D&D allows DMs to create their own villains as part of homebrew campaigns, so they don't need to use the established ones from the official books. There are a few recurring villains in the D&D multiverse that make appearances in adventures, such as Count Strahd of Barovia, or Acererak and his deadly tombs. Vecna also appeared as a foe in D&D adventures, as players can take a shot at him in Vecna Lives!, but they are spared from a magical beating by the arrival of Iuz, an evil demigod who intervenes and takes on Vecna himself. Vecna was already one of D&D's best (and most powerful) evil villains, and this was before he became a god.
Vecna was once a human king, who transformed into a lich, by placing his soul into an object and embracing undeath as a means of immortality. His schemes eventually led to Vecna's ascension as the god of secrets in the Greyhawk campaign setting, and he did so while missing two limbs. Vecna was betrayed by his lieutenant, the vampire Kas, who used the mighty Sword of Kas (one of the few +6 weapons in D&D) to slice off one of Vecna's hands and tear out one of his eyes. This brutal battle had the unintended side effect of unleashing chaos on the multiverse, as Vecna's lost limbs went on to cause trouble of their own.
D&D - Vecna's Limbs Are Stronger Than Most Magic Items
A D&D party is unlikely to encounter Vecna, but there's a chance they will find his missing body parts. The Eye of Vecna and the Hand of Vecna are two of the strongest artifacts in D&D, as anyone who is willing to tear off their own eye or hand and replace them with Vecna's lost limb will gain incredible power, at the cost of their very soul, as the artifacts will slowly seduce their wielder to the path of evil, and will have them within Vecna's thrall. D&D fans can collect Vecna's eye and hand, as WizKids made replicas of them, but a D&D party that finds one can find itself torn apart. The reputation of these items precedes them and many good adventurers would want to destroy the Eye or Hand of Vecna, but there is always the temptation of power. More importantly, the player will be tempted, simply so they can brag that they used these famous items in a campaign.
The limbs of Vecna were first mentioned in an early D&D sourcebook called Eldritch Wizardry, which was released in 1976, but little was mentioned about the character. The details about Vecna's backstory weren't realized at that time, but they were fleshed out in subsequent sourcebooks, adventures, and editions. Vecna went from a character who had powerful magical limbs, to one of the greatest threats in Oerth, to a god that is feared across the D&D multiverse. There are even rumors that Vecna will be in the D&D movie as a villain, but these have yet to be confirmed. Vecna is one of the longest-running Dungeons & Dragons villains, and he's a great choice to appear as an antagonist in a mainstream movie or show.