There were many reasons for the destruction of Arad, and the most famous one was the Cataclysm in World of Warcraft. During the Cataclysm, a fierce war broke out between the Alliance and the Horde near the Dark Portal. In this war, both sides used weapons of mass destruction, causing the entire Arad Continent to fall into ruins. Many towns and villages were destroyed, and countless people were displaced. The entire continent fell into chaos. According to the background of the story, the Great Calamity was triggered by the power from the shadow realm. These forces came from the Dark Temple near the Dark Portal. Due to the destruction of the Dark Shrine, the power of the shadow realm went out of control and spread to the entire Arad Continent. In the end, Arad was destroyed and many players were forced to leave the game to create a new world. As for who did it, it was not clearly stated in the background of the story. However, according to the plot settings of some novels and games, it might be thought that the Cataclysm was caused by a series of events and conflicts, not necessarily caused by a specific character.