Which expansion introduced the player housing Garrison system?

The Warlords of Draenor expansion introduced the player housing Garrison system. Garrisons were personal, upgradeable bases that players established and managed on the alternate-world version of Draenor.

The system became a central feature of the expansion’s questing experience. Players could construct buildings such as barracks, stables, an armory, and profession-focused structures, then recruit followers to undertake missions that returned experience, equipment, and other rewards. Garrisons also provided access to storage, crafting, vendors, and other conveniences.

Warlords of Draenor was released in November 2014 and raised the level cap from 90 to 100. Its story followed Garrosh Hellscream’s escape after Mists of Pandaria and his attempt to create an alternate Iron Horde on Draenor. Players visited their faction’s base throughout the campaign, making the Garrison more than a cosmetic home. Mists of Pandaria had introduced the farm at Halfhill, but that was a smaller precursor rather than the full Garrison system.