For the record, I don't hate spell slots. I think it's a fine design, and I'd happily run a game with them. The problem is at my table players do not like to pick a caster, and the reason is always the same. They look at the slot column, they know they will spend the best spell by the second fight.
So I tried to build something that keeps the choice and drops the budget. It has been running for a while now at levels 1 to 10, one group through level 10. The starting idea, fatigue instead of slots, is borrowed from a Brazilian game called Arcana Primária, which I'm crediting because it's someone's design. Nothing from their book is reproduced here, and nothing from Paizo either.
The rule
You don't have spell slots. You have a number called Magic Fatigue, and it gets added to the DC of casting.
Effective Casting DC = base DC for the rank + your current MF + Repetition Strain
You roll d20 + level + proficiency + key ability, plus 2 if the spell was prepared or is in your repertoire, against that DC. Success, the spell happens. Failure, it doesn't, and fatigue goes up. MF floors at 0 and caps at 10.
Rank categories come off your highest rank: High is your top rank and the one under it, Mid is one below that, Low is everything else.
| casting check |
High |
Mid |
Low |
| crit success |
+0 |
-1 |
-2 |
| success |
+2 |
+1 |
-1 |
| failure |
+3 |
+2 |
+1 |
| crit failure |
+5 |
+4 |
+2 |
Cantrips never roll. A two action cantrip removes 1 fatigue, guaranteed, even if the target resists or the attack misses. That line is the whole recovery system. A tired caster is not sitting out, they are casting small and getting safer, and then they can push again.
Things I'd call the interesting parts:
On a normal failure you choose: eat it, or Forced Effort, where the spell works anyway and you pay 2 more. Not available after a critical failure.
Cast the same spell at the same rank twice in a fight and every later copy gets +2 DC and +1 extra MF, stacking. Prepared casters get out of that by preparing a second copy. Spontaneous casters get one free repeat per rank. Signature spells don't give you more ammo, they give you the spell at other ranks, which is how you dodge the strain by moving sideways.
At 10 fatigue you can't attempt checked spells, and you can burn hit points instead: free action, fatigue drops to 4, Drained up 2, no daily limit, the limit is your body. That is the answer for the player who says "but what if I just want to keep going".
The Foundry VTT Macros
It needs a counter. I know that. Running this on paper means tracking one number per caster per fight, and if nobody at the table wants to do that, the system will drift and the caster will say "I think I'm at like 5". In practice a d10 next to the sheet works.
The Foundry macros do it properly. Two Script macros: the caster picks a spell off their real spellbook, the macro rolls the check, applies the fatigue, tracks which spells have been repeated, prompts Forced Effort, and posts the spell card without spending the slot, because in this system a slot is not a resource. There is one d20 for the casting check and the spell attack, a Hero Point prompt that shows your current result before you spend, a Counterspell flow, and a separate Spellstrike macro for the Magus that compares one strike roll against AC and against your casting DC.
Repo, with the quickstart, the full rules and the macros:
https://github.com/Thilaq/Escalating-Spellcasting/
Also: this is not a conversion of every option in the game. I converted what I thought I should, Divine Font, the wizard's bonded item, the three arcane theses (Spell Substitution, Staff Nexus, Spell Blending), Studious Spells, the Spellstrike, the eidolon feats, the Animist's two spellbooks, staves, wands and scrolls. Counterspell got one line rather than a conversion, it's the game's rule plus what you pay in fatigue. Bard, Druid, Oracle, Sorcerer, Witch and Psychic have a paragraph of guidance each, not a per-feat audit, and archetypes are barely touched. For anything I missed the full rules have one line for the GM to convert it on the fly, and that has held up so far.
What I want to know
Is the critical failure column too steep above level 10? I have no play above 10 to check it with.
And whether Refocus should be as free as it currently is. Fatigue clears to zero after 10 minutes of downtime, once per hour, riding on the game's own Refocus activity.