Forbidden knowledge (“taboo”, “proscibed”, “prohibited”) is knowledge that is only understood by the most rigorous and practiced. It is generally not taught as part of standard education or learning, but the concepts and activities rely on a more integrated set of information. Sometimes it takes a more advanced discovery process to garner the knowledge, or it may be revealed as insights through mastering all previous capabilities. Among skilled professions, such levels of knowledge are not taught as they are considered too risky and dangerous.
Forbidden knowledge is specifically not taught because it is considered too risky or its outcomes unpredictable and dangerous. They may be mentioned as part of training, education or discovery but mostly in passing, and teachers typically reinforce this by passing on warnings. It may not require any deep insight or it may require only what a masterful practitioner brings with them in terms of both academic and practical knowledge. Forbidden knowledge of extreme power and matching danger in acquiring or using it is often framed or referred to as black gnosis – the maddening knowledge of that which should not be known.
Forbidden Knowledge is knowledge that is derived by means of manipulating powers of The Void. It is anathema and dangerous. There are multiple levels of forbidden lore: Lovigdril (twisted by The Void) and Lovignhal (understood through The Void). The former has many formal practitioners – it is used as a shortcut in the path to understanding and knowledge by those with (typically) lesser affinity and aptitude. The later assumes that the seeker possesses not even rudimentary foundations to understand the knowledge (such as a magus seeking spells), but passes the consciousness of the seeker through the Void to impart such faculties. It is through this means that powerful magical abilities are made available to those who seek them – usually at the price of madness. Sanity is drawn on in the place of other energies to fuel such powers. More often than not, it is powerful artifacts (tomes, machines, constructs. etc.) built by entities of The Void seeking to siphon essence from the Aether.
Only the most desperate seekers of power plumb these depths. The lure of great power outside the constraints of affinity and aptitude is often too much for those who travel down the path, leading most often to madness and suicide. Powers normally beyond the ken of creatures can be made available. This knowledge is usually presented in a means which entails both ceremony and ritual, due to the alien thought processes required.