The Curse of Cabin Nine is a supposed curse that was put on the Hephaestus' cabin after demigod Charles Beckendorf died. In theory, the Curse of Cabin Nine denied all children of Hephaestus the ability to make any type of gadget, item, or automaton. In other words, not one project undertaken by Cabin 9 was successful.
The curse can go back to when Charles Beckendorf found the bronze dragon in The Demigod Files. Going on a detour from playing a game of Capture the Flag, some Myrmekes dug it up and took it to their hole. Beckendorf, along with Percy Jackson, Annabeth Chase, and Silena Beauregard, went in after it. Eventually they re-made the dragon and it managed to kill the Myrmekes, but then began to attack them. Beckendorf deactivated the dragon, but it was reactivated sometime between then and The Lost Hero.
Death of Charles Beckendorf
During a mission, Charles Beckendorf died in an explosion. He was one of the greatest children of Hephaestus, and this hit the cabin hard. After his death, this curse began affecting the cabin. All of Hephaestus' children had bad luck. None of their machines worked and the Bronze Dragon began to go crazy.
After Leo Valdez arrived at camp, he heard of the problem. He did not want the bronze dragon to be destroyed, so he began disabling the traps. The dragon showed up. Leo was a fire user, so he was able to fix the dragon without getting hurt. The dragon was fixed and Leo went on a quest, and when he returned, he became the Head Counselor of Hephaestus' Cabin. As a result, the curse was broken.