Ji Tiansao revealed the reason.
He was randomly teleported to the Evil God Sect's headquarters due to a misfired curse. Although he managed to escape immediately, he was still pursued by an emperor-level Slaughter Monarch.
The Slaughter Monarch, an evolved form of the Slaughter King, usually stands fifty meters tall and looks like a giant.
Even though he escaped from the Slaughter Monarch with the help of the Ten Thousand Crows Pot, he was hit by the Slaughter Monarch's skill "Evil Persona" before escaping.
The Evil Persona can split an evil personality from Ji Tiansao's soul.
This evil personality was the main culprit behind the cracking of the Ten Thousand Crows Pot.
The evil personality briefly gained control of Ji Tiansao's body, and he did something Ji Tiansao would never dare to do in his life... he contracted thirteen contracted beasts in one go, using up all the remaining contract slots.
