This skill, called soul contract, is a mandatory contract skill.
After mastering this skill, the caster can make a mandatory contract with the caster, and it is still an advanced contract among the contracts. There is almost no way to dissolve it.
Once the caster dies, the caster will perish with his soul. This kind of contract is extremely overbearing.
Of course, the soul contract is not omnipotent.
Its application has clear and strict regulations.