I'm looking for the identity of an RPG I remember reading in paperback book form (rather a thick tome), must have been published late 80s–early 90s.
A distinguishing feature was that while many (or in fact nearly all?) character “classes”* had specific magical/psionic abilities, they all depended on a further class of characters whose only role was to “enable” aforementioned “casters”. I think the enablers were called conduits or catalysts.
* Please excuse the heavy use of quote marks. I'm not sure of the exact terminology and I remember that the background actually avoided typical fantasy/sci-fi nomenclature (maybe that's another distinguisher if I remember rightly!)