Since the beginning of the series, Stranger Things has constantly made reference to Dungeons & Dragons. From the very first episode featuring Mike and his friends playing through a tabletop session to major enemies being named the Demogorgon and the Mind Flayer, Dungeons & Dragons has always been an integral part of the show. With its latest antagonist, Vecna, Stranger Things makes a reference to the tabletop game's most infamous villain and pulls inspiration more directly than ever.
For what it's worth, Stranger Things has tended to base its creatures only vaguely on their Dungeons & Dragons counterparts. The Mind Flayer in Stranger Things, for instance, bore almost no physical resemblance to its namesake, but possessed an affinity for mind control and psionic powers similar to the Mind Flayers from Dungeons & Dragons. When it comes to Vecna, however, Stranger Things pulled more closely from the game than it ever has.
Comparing The Powers of Both Vecnas
The original Vecna is arguably the strongest being in all of Dungeons & Dragons at his peak. While Vecna from Stranger Things boasts impressive proficiency in mind control and psionic magic that makes him at a potentially world-ending threat, Vecna from Dungeons & Dragons literally ascended to godhood, cementing his place as one the most powerful magic users in existence - a multiversal threat.
Vecna of Stranger Things borrows a few spells from his namesake, but shows significantly lesser magical abilities. Despite wreaking havoc on Hawkins, Vecna's abilities are fairly typical of a low-level spellcaster in Dungeons & Dragons. For comparison's sake, the Hand of Vecna - which acts as a powerful magic item in Dungeons & Dragons and is literally Vecna's severed hand - grants its user finger of death, teleport, and a myriad of other high-level abilities that are on-par with feats shown by Vecna in Stranger Things. When used in conjunction with the Eye of Vecna, these artifacts grant the user access to the wish spell, which far exceeds anything shown in Stranger Things.
Comparing The Lore of The Two Vecnas
While Vecna's lore in Dungeons & Dragons has undergone a number of changes, the foundation has remained consistent. Vecna began life as either a human or half-elf before transitioning into a lich by studying dark magic. From there, Vecna formed a massive army, championed by his lieutenant Kas, in order to facilitate his ascension to godhood. Ultimately, Kas betrayed Vecna, resulting in Vecna never reaching his full potential, and the two aforementioned artifacts - the Hand and Eye of Vecna - came into creation.
Oddly enough, Vecna of Stranger Things shares a backstory that, while not couched in high fantasy, remains similar. After being corrupted by his preternatural powers, Henry Creel attempts to manipulate and recruit Eleven to join his crusade, but is sent into the Upside Down and turns into Vecna. In both cases, Vecna begins life as a talented yet darkly-inclined individual who undergoes a complete physical transformation in an attempt to achieve their true potential. They're both inevitably betrayed by someone they consider close to them, someone who was personally recruited to aid them.
Further, Vecna in Stranger Things bears a striking physical resemblance to Vecna from Dungeons & Dragons 5E, as both are sleek and undead, yet imposing figures. It's also clear that Vecna's enlarged left hand is a nod to the powerful magical item in Dungeons & Dragons that made the character so famous. While the Eye of Vecna may not be explicitly referenced in Stranger Things, Vecna's victims are often left with their eyes mutilated.