It's possible, with effort and patience, for someone to utilize the power demons possess,
Summoners are those who convince demons, through whatever means they see fit, to join them in a form of mutualism in order to achieve a common goal. While this allows the benefit of a shapeshifting cohort to help you and keep you company, not all demons can be trusted to keep their word, or follow it in the way you'd hope.
Warlocks, meanwhile, utilize the power more directly by channeling it either on the behalf of a sufficiently powerful demon, or by stealing their semblance to use as an amplifier for spells. While you're guaranteed to get what you want, demonic semblance can impart aspects of the original demon's mind onto the user, altering their perception and mannerisms if the caster loses focus.
