The Western Revolver Man was a infiltrator within the Dark Conspiracy. He came from the Western World, and also was the one who discovered the evidence of Dumbeldore's innocence. He appeared in season 21.
IN SEASON 21:
The Western Revolver Man wanted to help Puck and Guus to stop the conspiracy. He infiltrated within the death eaters and the militairy soldiers and discovered that Red Eater, one of the death eaters with red clothes, who was also infiltrating in the conspiracy.
The Western Revolver Man also had the proof of Dumbeldore's innocence, which kept him out of Azkaban. After becoming friends of Red Eater, First Prince, Second Prince and The German Guest there real identity was discovered. On a camp they where trying to escape, but found by Bombers and all infiltrators, including The Western Revolver Man, where killed.