In High School DxD, the demons need to make a contract (a contract is formed after a demon fulfilled his/her purposes of the summoner) with someone to gain something.
What does a demon gain by forming a contract with the summoner?
In High School DxD, the demons need to make a contract (a contract is formed after a demon fulfilled his/her purposes of the summoner) with someone to gain something.
What does a demon gain by forming a contract with the summoner?
What the demon gains is dependent upon what the demon is willing to trade. When Issei is conversing with Azazel for the first time in Azazel's apartment, Azazel offers his soul to Issei, as this is something that demons have been depicted to want. However, Issei declines and accepts a painting instead.