The aging orc shaman Ner'zhul has seized control of the Horde and reopened the Dark Portal.

His brutal warriors once again encroach upon Azeroth, laying siege to the newly
constructed stronghold of Nethergarde Keep. There, the archmage Khadgar and the
Alliance commander, Turalyon, lead humanity and its elven and dwarven allies in
fighting this new invasion. Even so, disturbing questions arise. Khadgar learns of
orcish incursions farther abroad: small groups of orcs who seem to pursue a goal
other than simple conquest. Worse yet, black dragons have been sighted as well, and
they appear to be aiding the orcs. To counter Ner'zhul's dark schemes, the Alliance
must now invade the orcs' ruined homeworld of Draenor.