The scenario was developed with the World Editor of Warcraft III: Reign of Chaos, and was updated upon the release of the Warcraft expansion The Frozen Throne. There have been many variations of the original concept; currently, the most popular is DotA Allstars, which has been maintained by several authors during development. Since its release, Allstars has become a feature at several worldwide tournaments, including Blizzard Entertainment's BlizzCon and the Asian World Cyber Games, as well as the Cyberathlete Amateur and CyberEvolution leagues; Gamasutra declared that DotA was perhaps the most popular "free, non-supported game mod in the world".
Each human player controls one Hero, a powerful unit with unique abilities. In Allstars, players on each side choose one of ninety heroes, each with different abilities and tactical advantages over other heroes. The scenario is highly team-oriented; it is difficult for one player to carry the team to victory alone. Nevertheless, some heroes, given enough time, can change the outcome single-handedly, while countering the opposing team's heroes. Defense of the Ancients allows up to ten players in a five versus five format and an additional two slots for referees or observers, often with an even number of players on each side.
Because the gameplay revolves around strengthening individual heroes, it does not require one to focus on resource management and base-building, as in most traditional real-time strategy games. Killing computer-controlled units earns the player experience points; when enough experience is accumulated, the player gains a level. Leveling up improves the hero's toughness and the damage it can inflict, and allows players to upgrade their spells or skills. In addition to accumulating experience, players also manage a single resource: gold. The typical resource gathering of Warcraft III is replaced by a combat-oriented money system; in addition to a small periodic income, heroes earn gold by killing hostile units, base structures, and enemy heroes. Using gold, players buy items to strengthen their hero and gain abilities.
Certain items can be combined with recipes to create more powerful items. Buying items that suit one's hero is an important tactical element of the scenario. Allstars offers a variety of game modes, selected by the game host at the beginning of the match. The game modes dictate the difficulty of the scenario, as well as whether people can choose their hero or are assigned one randomly. Many game modes can be combined (for example, an easy difficulty level and a random hero pick), allowing more flexible options.
The scenario is popular in many parts of the world; in the Philippines and Thailand, it is played as much as the game Counter-Strike. It is also popular in Sweden and other Northern European countries, where the Defense of the Ancients-inspired song "Vi sitter i Ventrilo och spelar DotA" by Swedish musician Basshunter reached the European 2006 charts at #116 and cracked the top ten Singles Charts in Sweden, Norway, and Finland. LAN tournaments are a major part of worldwide play, including tournaments in Sweden and Russia; however, due to a lack of LAN tournaments and championships in North America, several teams have since disbanded. Blizzard points to DotA as an example of what dedicated mapmakers can create using developer's tools.