Daemons are malevolent spirits that inhabit the astral plane. This religion views these spirits as divine beings and worship them as gods. They are heavily revered in the faith, and are considered higher life-forms that are superior to humanity. Daemonology is the study of these creatures in order to use them for their power. This craft exists in two forms of study: The path of the summoner, and the path of the host. Both of these disciplines have their strengths and weaknesses, and are a reflection of daemonic society: that of constant improvement over one's self through ruthless individualism and subjugation of the weak. The only law is power, which must be used to acquire resources at the expense of the innocent. This is the only way to run a proper society.
The path of the summoner involves the torture and enslavement of daemons in order to bind them to the will of the practitioner, the practitioner can wear the daemon like a glove or a second skin. At this point, the daemons powers and abilities can be exploited, with the user calling upon them as needed. The daemon can even be summoned entirely, separating itself from the host to use its true power at the behest of its master. This path is multi-faceted, with users gaining access to the abilities of numerous daemons. Several creatures can be bound at once, with the most powerful users able to enslave dozens of daemons in this fashion.
The path of the host involves the same process of subjugating a daemon, but involves binding it to a user's soul, turning the practitioner into a daemonhost. This daemon-human hybrid is a demigod representing the best parts of mortal and divine. This path focuses on specialization, with the individual gaining access to one set of powers. However, those abilities grow with time, making the user more powerful.
Obviously the best goal that can be realized would be the combination of both paths. This would lead to a daemonhost that can control other daemons. This would be the ultimate dream for any practitioner, as it would lead to UNLIMITED POWAH. Sadly, this would be too OP, as the resulting being would kill everything on the map. However, no respectable student of the paths would shy away from achieving more powah for themselves, as not doing so would betray everything they stand for. The only way to prevent this is to design some way to prevent this from happening. How can this be made possible?