Some people are known as Spirit Users. These people are able to create contracts with Spirits.
InformationEditSpirit Users are in general really rare. Spirit Users are able to create contracts with Spirits, Quasi Spirits and Artificial Spirit's. People are only able to create a Spirit Contract when the user's gate is strong enough to substain a entire spirit inside of them.
Some Spirit Users are able to use their Od as a gate, which is really dangerous and has a chance to stop your heart from working.