Branch and the academy

A while back.

Ken had obtained a skill named [Devil God], the description of the skill was considerably simple since it only mentioned about him gaining the ability growing stronger through soul contracts, just like the Devils and demons he had heard of, back on Earth.

[[Devil God]: Ability to grow stronger by making deals with souls. [Souls contracts: ----] [Condition: Affirmation from the targeted entity]] [Restriction: Honest Promise]]

The skill was pretty good considering what he had been through to obtain it. Even if the skill was considered good, he couldn't just use it without understanding its limitations that weren't listed in the skill description completely, hence he had tested it on a few people and found out that if he had lied about the promise while offering a deal, the deal would be considered invalid. And, no matter what kind, as long as it was an affirmation from the targeted entity, the contract would be valid.