The Five Foundational Disciplines of Psykery - Pyromancy, Biomancy, Telepathy, Telekinesis, and Divination - each encompass foundational forces of the Warp; the forces of Energy, Life, Will, Space and Time, respectively. Each of these may be harnessed directly through both Warp Energy and the well of power that each Psyker contains within their soul. Even with the Warp in such a tumultuous state under the mismanagement of the Four, with the right mindset and control, one may wield these powers and still remain pure.
Daemonology, then, is often considered the odd one out. A most temperamental and frustrating Discipline, it encompasses an assortment of powers that have little bearing with one another, be they the arts of teleportation, the banishment or invocation of Daemons, the power to phase through objects or even the conjuration of a vortex in space into the twisting nether not unlike the results of a Vortex Grenade. It is often theorised by Masters of the Psychic Arts, of the Adeptus Ad Astra Telepathica or independent covens alike, that Daemonology is the sixth foundational Discipline, one that rests upon the Foundation of the Veil that divides the Materium from the Immaterium, and as the Veil is often fickle and the Warp so hostile it is consequentially the most difficult and dangerous Foundation of all.
They are wrong. You know better than that. Daemonology is not the sixth Discipline, nor is it some further evolution of any of the five foundational ones. Daemonology is a different beast from those five, a pathway to powers both great and terrible. But what you know of the true nature of Daemonology is... not immediately available to you. You don't have the divine perspective needed to truly grasp the nature of this odd duck, and until you find your way back onto your Astral Throne or find someone who does know the truth, you're out of luck. However, just because you don't understand the foundational principles of Daemonology does not mean you do not understand the dangers and effects of it.
Daemonology is, bluntly stated, tainted. The Warp is currently stained with the colours of the Chaos Gods, and the theory of Daemonology painting it as a Discipline of the Veil are not entirely unfounded. With the Warp as hateful and dangerous as it is, Daemonology is a dangerous path to walk for all the temptations that the Gods whisper and the black sewage that practitioners channel through their souls. Even Sanctic Daemonology, deemed 'clean' by the Grey Knights, is a dangerous path, for it is Malefic Daemonology but shackled. One who learns Sanctic Daemonology at the feet of the Grey Knights could easily twist that knowledge into an invocation of the Dark Gods, which is definitely why the Grey Knights so jealously guard the knowledge.
What you practice as Sanctic Daemonology is similar yet more, but also at the same time different. It's difficult for you to explain at the moment, but your brand of Sanctic Daemonology surpasses the understanding earned by the Grey Knights by leaps and bounds. You are far more capable at banishing Daemons, inflicting lasting wounds upon them and even invoking True Death, a fate all Daemons fear, for all their bluster of eternity. In theory you can also use it to traverse the Warp, form gateways into it and more easily explore it, but you do not want to know if your presence in the Warp can be determined like that yet, or even ever. Crucially, though, your brand of Sanctic Daemonology can be used protectively as well, forcefully calming the Warp and protecting others from the backlash of improperly channelled Warp energy, alongside smoothing travel in the Warp and other effects. In fact, you're fairly certain that your unique Divination style may actually be a form of Daemonology, from what you've tried to codify of the matter.
Daemonology is not the sixth Discipline, nor is it merely an assortment of powers plucked from the other five. It is something else. And it frustrates you to no end that you have a brain fart on this matter.