When I completed the mission, the scoreboard said these were the factions:
Zerg Swarm
Shelak Tribe
Leviathan Brood
Sargas Tribe
Correction: The Leviathan Brood is supposed to be zerg, which doesn’t exist in this mission. The Leviathan Brood is listed with a protoss zealot icon – so there might be something wrong in the database to have listed the Leviathan Brood here instead of a protoss tribe (Vanguard of Aiur).
In Zerg mission #9, earlier, Invasion of Aiur there was a third Vanguard of Aiur tribe: Zerinax Tribe. Maybe it should say Zerinax Tribe instead of Leviathan Brood.