In StarCraft, the Protoss hero who becomes a Dark Templar ally is Tassadar.
Tassadar begins as a Protoss Executor sent to contain the Zerg threat, but he eventually rejects the Conclave’s strict opposition to the Dark Templar. His alliance with Zeratul and the Dark Templar becomes essential to understanding the Zerg and resisting the Overmind.
This decision places Tassadar in conflict with Aldaris and the Protoss authorities. Tassadar’s willingness to combine traditional Protoss power with Dark Templar knowledge helps unite divided factions during the defense of Aiur.
Tassadar is distinct from Zeratul, who is the Dark Templar hero and his important ally. Fenix is another celebrated Protoss warrior, while Aldaris represents the conservative Conclave during much of the original story.