The series began in 2003 with the release of Defense of the Ancients (DotA), a fan-developed multiplayer online battle arena (MOBA) custom map for the video game Warcraft III: Reign of Chaos and its expansion, The Frozen Throne.

Ownership and development of DotA were passed on multiple times since its initial release until Valve hired the map's lead designer IceFrog and after a legal dispute with Blizzard Entertainment, the developer of Warcraft III, brokered a deal that allowed Valve to inherit the trademark to the Dota name.

A sequel to DotA, the game retains the same gameplay elements as its predecessor, while introducing new support and mechanics, as well as a setting separate from the Warcraft universe.

The original DotA map is considered one of the most popular of all time, with tens of millions of players and a consistent presence at esports tournaments throughout the 2000s.

Likewise, Dota 2 is cited as one of the greatest video games of all time, with an esports presence hallmarked by record-breaking prize pools that culminate in the annual championship known as The International.

[6] Unlike the original version, which is largely derived from the setting of the Warcraft series, the standalone games share their own continuity.

Heroes maintain special tactical advantages, in the way of their statistics, attack, and damage types, as well as abilities that can be learned and enhanced through leveling up from combat.

[10] Heroes battle alongside weaker computer-controlled infantry units periodically dispatched in waves, who traverse three paths called "lanes", which connect the Scourge and Sentinel bases.

[12] Valve's interest in the Dota intellectual property began when several veteran employees, including Team Fortress 2 designer Robin Walker and executive Erik Johnson, became fans of the map and wanted to build a modern sequel.

[20] Rob Pardo, the executive vice president of Blizzard Entertainment at the time, similarly stated that the Dota name belonged to the mod's community.

[15] Valve contracted major contributors from the Defense of the Ancients community, including Eul and artist Kendrick Lim, to assist with the sequel.

Development began in late 2014, with lead designer Richard Garfield being brought in to help make a digital card game due to his experience with creating the Magic: The Gathering franchise.

[37] While its gameplay and drafting mechanics received praise, it was criticized for its high learning curve and monetization model, which some likened to being pay-to-win.

[40] Dota Underlords is a free-to-play auto battler, a type of chess-like competitive multiplayer strategy video game, developed and published by Valve.

[53] A court document regarding the ownership of the Dota intellectual property from April 2017 confirmed Ismail as the identity of IceFrog, as well as his pre-Valve contributions in Heroes of Newerth.