|Pro tip: If you ever see a non-RPG book that talks about a
“blank rune”, throw it in the trash. There ain’t no
For instance, magic-users in AD&D have spells such as explosive runes, clerics have glyph of warding, etc. Some spells require gestures, others incantations, others material components, and most a combination of the three. Magic in the (A)D&D world is not divided by method, but by result. Thus, a magic-user can use runes in one spell, swallow a live carp for another, and rely on words alone for another.
Because of this, one must be very careful when attempting to come up with new sub-classes of spell-casters. My own Necromancer class fits, if I may say, very well with the current system because it doesn’t presuppose a brand new system of magic, but merely comes up with a new class whose uniqueness is defined by the spells to which they have access. The same with the witch sub-class; it’s a sub-class of cleric, but it doesn’t try to create a new system of magic to obtain its effects; it finds its uniqueness in the spells that the class is allowed.
It could certainly be a valid approach to simply fold those new spells into the existing classes, and define sub-types of spell-casters not by class delineations but simply by limiting their spell lists (in the case of magic-users, this is easily done by simply not making certain spells available due to in-campaign limitations, in the case of clerics, it is done by tailoring the spell lists of priests of different deities or faiths).
In the case of Advanced Dungeons and Dragons (and Adventures Dark and Deep™), that’s not the design decision that was made, but it’s certainly a valid way to go. It’s one of the chief reasons, I believe, that subclasses like the chronomancer, rune-caster, and so forth don’t really ring true. What’s needed is not a new type of magic, but a unique emphasis on results.