I'm definitely someone where the term conjurer summons up images of dark robed ritualists summoning up demons and elementals for power thanks primarily to all of the old Conan the Barbarian and other sword and sorcery books I've read over the years. I think it would be good to split the current conjurer subclass into two, one focused on summoning, the other teleportation.
I think this is a great thing to look at and think about...
As I said above, the "specialist school" structure as/for "Wizards 31 flavors," it might be very cool for the next edition (and other systems) to take the various flavors of specialists and make them different casters...not just different "wizards."
To pull in the mechanical differentiations suggested by the OP, and elaborated/added to by myself, we'd have a game wherein you have something like:
"Evokers": The "Full caster," spell levels (cantrip) 1-9, from 1st level
- Arcane: The Mage (nee wizard): Spells, spells, and more spells. All the spells. Magic Use is their thing. They use magic, primarily through spells. Slot progression. Combination spell prep and spontaneous selection mechanic added at higher levels.
- Psychic: The Psychic (nee "psion"): Mental Powers: telepaths (communications, direct mind attacks/defenses, illusions), empaths (healers & emotion control/support), telekinetics ("force" mages, specific element kineticists), clairvoyants (seers, psi-rogues). Point progression. Accumulate different powers, tricks/stunts that can be done with those powers, use as much as you want as long as you have the points to do so.
- The Illusionist: straddles the magics betwixt arcane and psychic with enchantments, phantasms, mind influencing/warping.
- The Witch: spell list straddles arcane and nature spells, plus innate supernatural powers ("Witch's Crafts"), access to alternate types of spells (arcane and divine), psychic abilities, and occult powers through features, potions.
- The Conjurer: spell list straddles arcane and divine spells, plus ritual and diagramatic use of non-divine magics, "ceremonial magics," binding circles/diagrams, et al, conjurations (of spirits, demons, undead, etc...)
"Invokers": The "3/4 caster," Channeling powers from 1st level, spell levels 1-6, from 3rd level:
- Divine: The Cleric: Channeling Divine powers (turn undead, sense divine, domain power) at 1st level. Additional channeling powers (by class or domain) 2nd level and every 4 levels after. Spell use: 1st level spells at 3rd level, caps 6th level spells at 13th level.
- Nature: The Druid: Channeling Nature powers (pass without trace, sense nature, shapeshift, etc...) at 1st level. Additional channeling powers (by class or domain) 2nd level and every 4 levels after. Spell use: 1st level spells at 3rd level, caps 6th level spells at 13th level.
- Psychic: The Oracle/Diviner: Channeling Mental powers (auger, sense mind, devotion power) at 1st level. Additional channeling powers (by class or devotion) 2nd level and every 4 levels after. Spell use: 1st level spells at 3rd level, caps 6th level spells at 13th level.
- Arcane: The Theurgist: Channeling Arcane powers (summon servant, sense magic, circle power) at 1st level. Additional channeling powers (by class or circle) 2nd level and every 4 levels after. Spell use: 1st level spells at 3rd level, caps 6th level spells at 13th level.
"Occultists": The "Half caster," Channeling powers and cantrips from 1st level, spell levels 1-5, from 3rd level:
- Arcane: The Warlock: Channeling Arcane Energies (eldritch blast, sense magic, patron power) at 1st level. Additional channeling powers (by class or patron) 2nd level and every 3 levels after. Spell use: Cantrips at 1st level, 1st level spells at 3rd level, caps 5th level spells at 15th level, additional/different spells by channeling/patron powers.
- Divine: The Shaman: Channeling Spirit [World] powers (entreat aid, sense spirit, etc... ) at 1st level. Additional channeling powers (by class or patron) 2nd level and every 3 levels after. Spell use: Cantrips at 1st level, 1st level spells at 3rd level, caps 5th level spells at 15th level, additional/different spells by channeling/spirit powers.
- Nature: The Bard: Channeling Nature powers (inspire courage, sense trouble, college power) at 1st level. Additional channeling powers (by class or college) 2nd level and every 3 levels after. Spell use: Cantrips at 1st level, 1st level spells at 3rd level, caps 5th level spells at 15th level, additional/different spells by channeling/college powers.
- Psychic: The Ascetic/Shukenja: Channeling Chi/Ki powers (stunning fist, sense danger, devotion power) at 1st level. Additional channeling powers (by class or devotion) 2nd level and every 3 levels after. Spell use: Cantrips at 1st level, 1st level spells at 3rd level, caps 5th level spells at 15th level, additional/different spells by channeling/patron powers.
"Dabblers" (working title): The "Third [Quarter?] caster," if such things are necessary to differentiate, Non-spell supernatural powers from 1st level, spell levels 1-3, from 5th level:
- Arcane: The "Eldritch Knight"/spellblade/what have you arcane fighter-mage dude: enchant(ed) weapon, sorcerous strike (arcane smite), sorcerous shield, minimal arcane spell use
- Divine: The Paladin: same ole typical paladin divine powers, channelled smites, minimal divine spell use
- Nature: The Warden: magical ranger, nature channelled powers (including shapeshifting), "primal strike" (nature magic smite), minimal nature spell use (the standard Ranger class should be spell-less!)
- Psychic: Either the Psi-warrior "Jedi" dude or the standard chi-manifesting Monk.
Random Aside******
Honestly, I lean more and more every year toward "Necromancer" being a prestige-style class. Define "Necromancy" as magic-working with the energies/powers of the negative energy plane, real "Dark Wizard" stuff. This makes it a sort of "forbidden" thing that just about anyone who can use magic (mages, clerics, warlocks, theurgists, even druids...) can "fall into" or become ensnared by (or purposely enamored with)...and eventually corrupted and turned evil, even if that isn't their original intent.
For the "what about a 'good necromancer'?" crowd...that has only and always been an oxymoron to me. And I've played with my share...or, at least, neutral/"non-evil" aligned ones. BUT we can make a mirror image "Positive energy" focused magic-user. Same kind of prestige-class style set up that can be "added" to any other caster archetype. The flip-side to a "necromancer" that I like to call a "Vivoker." They study/find/are attuned to/practice "vivocation," the "positive energy, healing, radiant damage, life magic" stuff.
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