Which StarCraft II game focuses primarily on the Protoss campaign?

StarCraft II: Legacy of the Void focuses primarily on the Protoss campaign.

Released in 2015, Legacy of the Void concludes the main StarCraft II trilogy. Its story follows Artanis, the Hierarch of the Daelaam, as the Protoss attempt to reclaim Aiur and confront the larger threat associated with Amon. The campaign is built around the Protoss flagship, the Spear of Adun, which serves as a mobile base between missions.

Wings of Liberty is the Terran-focused opening game, while Heart of the Swarm follows Kerrigan and the Zerg. Legacy of the Void also introduced new multiplayer units and major balance changes. Although all three games include multiple factions in their broader story, the campaign's principal viewpoint identifies this installment as the Protoss chapter.