A contract depended entirely on how the relationship between the contractor and Spirit progressed.
If their relationship was poor then a Spirit could get affected negatively.
If their relationship was a good one then a Spirit could become very loyal and remain in good Spirits.
If it was too negative then it would not be able to resist the influences pulling it towards becoming an Evil Spirit.
Once it had become an Evil Spirit, it was very easy for it to become aggressive and even turn on its owner once its contract was shaken during that time.
It was difficult to maintain a contract with the Spirit once it became an Evil Spirit due to it becoming an entirely new being that was no longer its former self.
Any former restrictions would be removed in its new state so nothing was stopping it from attacking someone it was once loyal to.
