Thats pretty similar to what 3e (and iirc older) counterspell did. You had to cast the same spell in reverse to counter a spell. So to counter spell a fireball, you had to have a fireball prepared and “counterspell cast” your fireball. That said, there was some action economy problems in 3e that made it not worth it (you had to use an action to ‘ready’ a counterspell on a specific target, when the target cast a spell, you had to roll to identify the spell, and if they cast a spell you didnt know or have prepared, you were out of luck)

Yeah, basically what older editions did. I also like that you have to identify it, too, so I keep that in.

If you prepared the exact spell that day, great, you identify it, and can expend a casting of that spell to counter it.

If it’s not something you prepared that day but it is something you could’ve prepared, maybe you recognize it. Free action to roll arcana (or, your spellcasting tradition, for pf2). For games with secret rolls, like pf2, this roll is secret.

However, I also like 5e’s counterspell as a preparedness check, so if i feel like some homebrew that day, I add a spell back in. Ive never settled on a good name for it so I’ll call it Read Spell here. What this version of the spell does is casting it as a reaction allows the same identification as above, but if it’s on your list and is your level, you automatically succeed. If its above your level, or not on your list but the right level, then it grants that roll.

So a level 5 wizard that prepped fireball could counter fireball, expending 1 level 3 slot.

A level 5 wizard with fireball in their book that didn’t prep fireball could counter it with a successful arcana check, and therefore could reasonably counter fireball, but isn’t guaranteed to be able to, for the same level 3 slot.

A level 5 wizard with fireball in their book that didnt prep fireball but that had the level 1 Read Spell could counter a fireball (or any other lebel 3 or lower wizard spell) guaranteed, and would end up spending that Level 3 slot and the slot for Read Spell.

A level 5 druid (no fireball) couldn’t succeed at countering Fireball without Read Spell, but could cast Read Spell to get a chance at that roll.

And a level 3 wizard could also get a chance in the same way, although they’d really only be able to use that if they were like, 3 wizard/2 cleric, something that gives them third level slots without third level spells. Niche, but valid I feel.

Despite this theorycrafting, I’ve never had a player even take counterspell or my homebrew options, even when they know they’ll have a wizard, so this remains untested.

My personal thought was to remove counterspell from all non-wizard spell lists and turn it into a wizard-only spell. That alone…

1. Makes wizards desirable over sorcerers, bards, warlocks, and some specific clerics.
2. Plays into their “I know more about magic than you do” magic-nerd-theme.
3. Makes counterspell far more rare.

I would probably make spells easier to interrupt like they were in 3e.

https://www.d20srd.org/srd/magicOverview/castingSpells.htm

These two things were key:

• Casting a spell provokes an opportunity attack
• Taking any damage requires a check or you lose the spell

Now casting when the orc warlord is up in your face is a lot riskier.

I think I get why they got rid of this system. It was more to think about, and I think they wanted the game to generally be easier so more players could enjoy it. Certain classes of player don’t want to think about tactics and positioning. They want to cast fireball. But as a result, the whole game is kind of shallower sometimes.

For mages countering mages, I’d probably give it a rework. It shouldn’t just be its own spell. It should be an action. Maybe have a separate check to identify the spell, or maybe just tell the player to skip double rolls. Then make some sort of opposed check. Use the spell level delta (and if you had them roll to identify, how thematically opposite the spell is. Like a fire and ice spell, or shield v magic missile).

I am not sure it would be any good. Basically it would mean the meta spells would be counterable like before, so the characters have an option to take less useful or more niche spells to avoid a counterspell.

But in practice counterspell is already constrained by memory slots, spellslots and actions (it takes a bonus action, which there is only one per turn), and also range and vision. It also takes identifying the spell to not waste your counterspell on something useless.

So I’m not sure what the intent could be with this. A wizard would basically be required to take fireball if only to counter it, and avoid using it against another wizard. It feels to me that it would decrease the possibilities, not increase them.

If remember correctly, DC20 does something similar but instead of the same spell you must use some other spell that would be a reasonable counter effect against the effect that the spell is trying to produce.