Any cultivator would know some large-scale magic spells. These magic spells might not be very effective on some cultivators, but they were still very destructive to things.
Zhao Hai and the others had already made an agreement with the cultivators in their team. If they had the chance to enter the ark of misfortune, a portion of them would block the people on the ark while the other portion would destroy it. They would do their best to cause large-scale destruction.
Those people remembered Zhao Hai's words. Hence, after they entered the ark of misfortune, they started to destroy everything they could see. They used all means to destroy it.
With so many people and so much power, if these people really did not care about anything else and only focused on destruction, the destructive power they could cause would be extremely terrifying.