Collected by the bagful and emblazoned on T-shirts, the 20-sided die is now ubiquitous as a talisman of geekdom. From its humble origins as gaming equipment to its present mainstream recognition, the history of the 20-sided die reflects the changing place of geek and fantasy media in culture.

 © Leland Renato Grigoli

Though museums like the Metropolitan Museum of Art and the Louvre house examples of 20-sided dice originating in Ptolemaic Egypt and ancient Rome, the modern version was developed first for the historical wargaming scene and then Dungeons and Dragons (D&D), the first and most popular tabletop fantasy role-playing game. In their quest for games that more realistically simulated historical armed conflicts, wargaming hobbyists in the 1970s created rules, which they shared in hobby magazines and newsletters. Often basing their rules on statistics derived from analysis of actual combat, these wargamers needed a means of resolving complicated odds. Fans instructed one another on how to use chits, homemade spinners, or decks of cards to model probabilities. Dice with more (or fewer) than six sides were one such method, but difficult to source until 1972, when an American educational supply company released a set based on the five platonic solids, including the 20-faced icosahedron.

At the same time, many wargaming hobbyists had exhausted the catalog of historical battles. Inspired by fantasy and pulp series like The Lord of the Rings, Conan the Barbarian, and Fafhrd and the Gray Mouser, they developed rules for fighting fantasy battles involving wizards and monsters, and then for playing as individual questing heroes. In 1974, when David Arneson and Gary Gygax revised these homemade rules into a game they could sell—D&D—they relied on the newly available polyhedral dice, though these still had to be purchased separately. D&D billed itself as a framework hobbyists could use to build their own game, and the dice reflected its DIY origins. Cheaply manufactured, the dice molds could fit only a single digit on each face, so rather than being numbered 1–20, they were numbered 0–9 twice. Players had to color in the numbers themselves, and the poor-quality plastic soon wore down to a sphere.

As D&D became popular in the early 1980s and new role-playing games emerged to compete with it, the publisher sought to make it a more standard commercial product. Subsequent rules revisions gave the 20-sided die an increasingly prominent place. The publisher also purchased and resold polyhedral dice (crayon included) alongside the rules, which gave players a game they could play out of the box and served as a hedge against piracy; written rules were easy to copy, but plastic dice weren’t. This process continued through the ’80s and ’90s, and soon both competing games and dice—now sold with numbers 1–20 already colored in—were widely available from other sellers.

The present mainstream recognition of the 20-sided die and D&D reflects the rise of geek chic. Fantasy series like The Lord of the Rings and Game of Thrones have spawned media franchises that bust budget records, while online streaming, podcasts, and Netflix’s Stranger Things have made D&D more popular than ever before. People who have never cracked a Monster Manual are now familiar with D&D foes like Demogorgon, Mind Flayers, and Vecna. Dice that were once hard-to-find specialty items are now available in a bewildering variety of colors from myriad sellers. Enthusiasts so inclined can spend over $100 on a single die made of solid tungsten and weighing nearly a pound, or $5,850 on the Hermès icosahedron (covered in leather with hot-stamped gold numbers). Like geek and fantasy media, the 20-sided die has risen out of the basement and into the mainstream.