There are areas of magic study universally banned by the Tradition of the Bound. It is worth noting that at the time of the introduction of the Treaty of Avalon, certain prominent old-blood Hexborn families such as Grey, Faust, Drachenberg, Artemis , Wychwood, and Twardowski had much of their influence from some of these arts. In spite of the political dimensions that might have been behind the decision, it is probably for the best that they did end up being prohibited from common use, given their potential for destructive use.
As a note, Otilia von Drachenberg was famously known to have said: “If you are concerned about potential abuse of power, why are you binding our Chronomancy while leaving the Mind Magic of our rivals unbound?” Without a doubt, this had quite a bit to do with the political prowess of the families primarily practicing Mind Magic, and in all honesty, Mind Magic is as dangerous and easy to abuse as the Bound Arts. While the study is not prohibited, the use of Mind Magic is strictly regulated by law in most confluxes.
Demonology is a rather potent and horrifying sub-field of Invocation. Where Invocation deals mainly with relatively benign and often helpful entities, Demonology plunges into the depths of the most infernal otherworlds, searching for powerful and malign beings and their undying service. While some of the basic concepts taught in the summoning regimen of Invocation can indeed be used for the purposes of Demonology, the exact secrets of how to perform a demon summoning remain vague to most. As a side note, summoning Fae, while it’s not exactly related to Demonology, may be equally dangerous.
Another extremely dangerous sub-field of Invocation (and some claim, of healing) is Necromancy, the manipulation of death itself. Typically it involves the raising of undead minions, or so legend has it. Those who are learned in the ways of Necromancy can suspend a sort of half-death for many hundreds of years, and trap ghosts and souls to do their bidding. These concepts tend naturally to freak out most non-Necromancers.
Chronomancy, a sub-field of Arithmancy, is also known by the more descriptive moniker of Time Magic. While this art is considered by some to be the “least evil” of the Bound Arts, others know just how disruptive and dangerous manipulation of time can truly be. Rogue Chronomancers are few and far between. Some say this is proof that they are in fact legion, only amassing just around the corner of history. Time will tell (maybe)!
Legal study of the Bound Arts does occur quite frequently under the heavy supervision of the Guardian Order. While purity of action might be commendable in some cases, it is next to impossible to fight a rogue practitioner of Demonology without knowing enough to perform an exorcism. It is equally impossible to untangle time manipulations without knowing at least the basics behind Chronomancy. As such, the Guardian Order is more or less forced to allow at least some exploration of these concepts.