General System of Dispelling and Counterspelling

[Catullus64]

The spells Counterspell and Dispel Magic are removed from the game.

Counterspell and Dispel Magic are now a generic Reaction and Action to be taken in combat.

Counterspell Reaction: When a creature within 60 feet of you that you can see casts a spell, you can attempt to interrupt it. Choose one spell of 1st level or higher which you are capable of casting, and for which you have an appropriately-leveled spell slot. You expend one such spell slot as part of this reaction. You then make an ability check with your spellcasting ability. If you succeed, the spell fails and has no effect. The DC of this ability check is equal to 10 + the difference between the level of the spell cast and the spell expended to counter it + the spellcaster's ability modifier.

Dispel Action: Choose any creature, object, or magical effect within range. Choose one spell of 1st level or higher which you are capable of casting, and for which you have an appropriately-leveled spell slot. You expend one such spell slot as part of this action. For each spell active on the target, make an ability check using your spellcasting ability. The DC of this ability check is equal to 10 + the difference between the level of the spell cast and the spell expended to counter it + the spellcaster's ability modifier. If you succeed, the spell ends.

School Opposition: The eight schools of magic sit in pairs of opposed relationships with one another; it is easiest to dispel or counter a spell from a specific school with a spell from the opposed school, and difficult to counter it with a spell from the same school. When you attempt to counter or dispel an effect, look at the following table to determine if the spells are of same, opposing, or neutral schools. If the spells are of the same school, the ability check you make to dispel or counter it has disadvantage. If the spells are of opposing schools, the ability check has advantage.



School
Opposing School


Abjuration
Transmutation


Conjuration
Divination


Illusion
Necromancy


Evocation
Enchantment

[JNAProductions]

On the one hand, it's neat.
On the other hand, that makes casters a lot stronger against other casters, since they can be counterspelling from a first level slot.

Not sure if I'd want it implemented in my games, but it's definitely a cool idea! The only thing I'd say absolutely HAS to happen is for you to provide an example, just so we can see properly how to make the DC of the check. I think I get it, but I'd want to be sure.

[Catullus64]

The only thing I'd say absolutely HAS to happen is for you to provide an example, just so we can see properly how to make the DC of the check. I think I get it, but I'd want to be sure.


DM: The hobgoblin mage begins chanting, and extends a finger. A bead of orange light begins to form at the fingertip.

Player (of Gilgalion the Bard): I'm going to use my reaction for a counterspell.

DM: Ok, what spell are you going to use to counter it?

Player (thinking): Safe money is on this being a Fireball. (Checks character sheet) Evocation, I think, and weak to Enchantment... I use Sleep!

DM: Roll a check using your spellcasting ability. With advantage.

Player: 17

DM: (Does quick arithmetic in head): The Devestator has an Intelligence mod of +3, and is casting a 3rd level spell... Sleep is 1st-level, 3 - 1 = 2. 10+3+2 = 15. (Thinks of description for a moment): Your hastily-cast spell produces an involuntary yawn in the hobgoblin, causing his spell to sputter out and fail.

This example is designed to match the level of description and information usually given at my table. At a table where the DM just says "the hobgoblin casts Fireball", this would be quicker. Most of my players are experienced enough to know or guess off the top of their head what school a spell is. If yours aren't and you don't mind the slowdown, you could allow an Arcana check to guess the school of the spell. Looking at the example above, I might also say that you have to meet the component requirements of the spell you intend to use for the counterspell.

If you do use this rule, I recommend amping up the threat that spellcasters present, to encourage its use.

Which schools are opposed to which is entirely a matter of personal preference, and can be adapted to whatever (if any) in-universe lore you have about the eight schools of magic. I just used the old opposition chart from AD&D.

[Twelvetrees]

With this system can you still counterspell a counterspell? I didn't think so initially but this line from your example has cast some doubt on that assumption.
DM: (Does quick arithmetic in head): The Devestator has an Intelligence mod of +3, and is casting a 3rd level spell... Sleep is 1st-level, 3 - 1 = 2. 10+3+2 = 15. (Thinks of description for a moment): Your hastily-cast spell produces an involuntary yawn in the hobgoblin, causing his spell to sputter out and fail.
Emphasis mine. If the Counterspell Reaction counts as a spell, counterspelling a counterspell is still an option. Can you clear up what your intention was?


In general, the major effect I'm noticing with this change is that automatically countering spells is no longer an option. I don't think that the difference in spell level will be enough of an incentive to get players to use high level spell slots to counterspell which means they can more effectively conserve resources. Doubling the difference in spell level when calculating the DC would make using higher level spell slots a much more attractive choice.

[PhantomSoul]

In general, the major effect I'm noticing with this change is that automatically countering spells is no longer an option. I don't think that the difference in spell level will be enough of an incentive to get players to use high level spell slots to counterspell which means they can more effectively conserve resources. Doubling the difference in spell level when calculating the DC would make using higher level spell slots a much more attractive choice.

I like using Spell Point Costs for this sort of thing, but it would just be an extra list if you don't reference them otherwise! (The scaling for double-level is better, though, and in this case that may be more appealing. I'd tend not to calculate the difference between slot levels ever; just add it on both sides to keep it simple.)