Starcraft 2, Legacy of the Void is an expansion to the original Starcraft 2.
Artanis is the main protagonist in the game. And the Dark God Amon is the antagonist.
The story of the game starts off with the beginning points of explaination of why the Protoss are at war. In order to find out the truth, Zeratul searches for the peices of the Xel’Naga prophecy. Zeratul travels to a region ruled by Terrans to help Praetor Talis a commander with Artanis to free captured Protoss. After freeing the captured Protoss, Zeratul travels to the planet Atrias. This planet has a Xel’Naga Temple. Zeratul forces through the temple. Zeratul destroys the Void Catalyst that prevents Amon from empowering Protoss units.