Warcraft III: The Frozen Throne is the expansion pack for Warcraft III: Reign of Chaos, a real-time strategy video game by Blizzard Entertainment. It was released worldwide on July 1, 2003 for Microsoft Windows and Mac OS X. The Frozen Throne builds upon the story of Reign of Chaos and depicts the events after the main game's conclusion. The single-player unfolds from the perspective of two new protagonists – the Night Elf warden Maiev Shadowsong and the Blood Elf prince Kael'Thas – as well as returning protagonist Arthas Menethil. Additionally, the expansion contains Act I of a separate Orc campaign that is independent from the main storyline with Blizzard releasing Acts II and III via patch in December 2003, taking in player feedback of Act I when developing these chapters. The expansion adds new units, buildings and heroes for each faction, two new auxiliary races, five neutral heroes (with three more later added by patches) as well as a number of tweaks to the gameplay and balancing. Sea units were reintroduced which were absent in Reign of Chaos. Battle.net-powered multiplayer was expanded by the addition of clans, automated tournaments and new maps and custom scenarios. Development began in October 2002, shortly after the release of the main game and the expansion was announced on January 22, 2003. Public beta tests allowed 20,000 players in two waves to try the new features. Support continues even after release, with Blizzard adding new content and balancing changes as well as support for newer hardware. The Frozen Throne received generally favorable reviews from critics with most reviewers praising the mission design of the single-player campaign for positively deviating from the standard real-time strategy game formula. The design and audio of the new units was generally considered fitting, though a few critics bemoaned the dated graphics and some of the voice-acting. By August 15, 2003, it had sold more than one million copies.