Aggramar is the titan disciple of Sargeras who discovered Azeroth for the Pantheon. They originally hunted together to stop the spread of demons. After Sargeras left the Pantheon, Aggramar created the titan-forged to fight the Void on behalf of the titans because direct combat could destroy Azeroth. His creations succeeded at defending the nascent world soul until Sargeras emerged eons later as the leader of the demons and initiator of the Burning Crusade.
In response to the destruction of a world, Aggramar confronted and directly challenged his former master to combat. Both of the titans shattered their enormous blades in a blinding explosion of fel and arcane. Heavily wounded, Aggramar retreated to alert the Pantheon about the demonic betrayal of Sargeras. Aggramar recovered and foolishly confronted his master, unarmed, attempting to end the dispute by diplomacy. Sargeras quickly ended negotiations by nearly cleaving Aggramar into two then slaughtering the rest of the Pantheon.
Fast forward to Argus, Sargeras corrupted the avatar of Aggramar and turned him into a pawn. Aggramar watched over the Shivarra as they tortured his former Pantheon comrades and attempted to break their minds. Fortunately, somehow the spirits of titans capable of destroying entire planets were no match for drunk ass Pirates. One by one, the Pantheon titans fell before the collective colossal might of Pirates until only Aggramar remained.
Based on knowledge of how Aggramar fell before Sargeras, the Pirates attempted to convince him that they would join the Burning Legion and help Sargeras to accomplish all of his evil goals. Aggramar always knew that he is a skilled diplomat and eagerly sheathed his sword while beginning to open a communication channel to his master. As soon as Aggramar turned his back, the Pirates zerged and stabbed him repeatedly in a grotesque scene more bloody than the murder of Caesar. After freeing Aggramar from Sargeras' grasp, he quickly came to his senses and thanked us for stabbing his spirit to death. Then he pledged to help the heroes of Azeroth against Argus the Unmaker at the Seat of the Pantheon.