Warcraft 3: Dota (Defence of the Ancients)

Defense of the Ancients (DotA) is a multiplayer online battle arena mod for the video game Warcraft III: Reign of Chaos and the second part Warcraft III: The Frozen Throne, based on the "Aeon of Strife" map of StarCraft. The objective of the objectives for each team to destroy the opponents' Ancient, heavily guarded Base(Kingdom) at opposing corners of the map. Players use powerful units known as heroes, and are assisted by allied heroes and AI-controlled fighters. As in role-playing games, players level up their heroes and use gold to buy equipment during the mission.

The scenario was developed with the "World Editor" of Reign of Chaos, and was updated upon the release of its expansion, The Frozen Throne. There have been many variations of the original concept; the most popular being DotA Allstars, which eventually was simplified to DotA with the release of version 6.68. This specific scenario has been maintained by several authors during development, the latest of whom is the anonymous developer known as "IceFrog" who has developed the game since 2005.

Since its original release, DotA 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; in a 2008 article of video game industry website Gamasutra, the article's author claimed that "DotA is likely the most popular and most-discussed free, non-supported game mod in the world". DotA is largely attributed to being the most significant inspiration for the multiplayer online battle arena genre. Valve Corporation acquired the intellectual property rights to DotA to develop and release a stand-alone sequel, Dota 2.

DotA pits two teams of players against each other: the Sentinel and the Scourge. Players on the Sentinel team are based at the southwest corner of the map, and those on the Scourge team are based at the northeast corner. Each base is defended by towers and waves of units which guard the main paths leading to their base. In the center of each base is the "Ancient", a building that must be destroyed to win the game.

Each human player controls one hero, a powerful unit with unique abilities. In DotA, players on each side choose one of 112 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. 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 equal 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, unlike most traditional real-time strategy games. Killing computer-controlled or neutral units earns the player experience points; when enough experience is accumulated, the player gains a level. Levelling up improves the hero's toughness and the damage they 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. This has caused emphasis on a technique called "last-hitting," which is when the player attacks a hostile unit when "its hit points are low enough to kill it with one blow". 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 mod. Item choice also affects play style, as any given item may increase one statistic while leaving another unchanged, or give unique abilities changing the playstyle of the hero.

DotA 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, allowing more flexible options.