DND_Reborn
The High Aldwin
My concern with many of the suggestions offered in this thread is complexity. The more rolls you add to a rule, the longer that rule takes to resolve. Since CS is a reaction, it really needs to be quick. Even the roll for for higher level spells is stretching the time taken to resolve this, so making it an opposed check is making things worse, not better IMO.
A whiplash/feedback mechanic seems like it could be a good, flavourful and fun idea but I am not sure it will be worth it. Especially if passing the CS check hits the original caster and failing hits the counterspeller. It's a net 0 effect (not mathematically I know).
As it stands casting CS runs the risk of using a 3rd level slot for no effect, which strikes me as a good risk/reward mechanism. When it comes to outright countering spells 3rd level and below I think that skipping the roll for a faster resolution is a simple way to keep things going when the effect of the countered spell will likely be minimal.
To me things look like this:
PC level 5/6: You're using your top level slots to lock down an enemy is a HUGE cost so should have big rewards - guaranteed success:
PC level 6 to 10: Using 3rd level spells is still quite a big cost so countering low levels spells seems fair while countering higher level spells comes at the risk of failure (a spell slot for absolutely nothing). Using higher level spells to guarantee success is trading power (high level spell slot cost) for certainty.
As you increase in level lower level spells become more trivial so I like seeing a quick resolution , while keeping some risk or cost when throwing out big guns.
The only change I would really think to be good would be to require the CS to be of a higher level that the countered spell. ie Casting CS at 3rd level would auto counter 1st and 2nd level spells. That way casting a 9th level spell always has a chance for success.
You have a good point about the speed of it. I am always looking for ways to speed up the game. An idea I just had (might tinker with it, might not) is to remove the roll and have counterspell automatically work but the caster takes damage as he stops the spell. I was thinking something like this:
Counterspell
3rd-level abjuration
Casting Time: 1 reaction, which you take when you see a creature within 60 feet of you casting a spell.
Range: 60 feet
Components: S
Duration: Instantaneous
You interrupt a creature in the process of casting a spell. If the spell level of the spell you interrupt is equal to or less than the spell level slot you use for Counterspell, you take psychic damage equal to twice the spell level of the interrupted spell. If the spell level slot is higher than the spell slot you use for Counterspell, you take psychic damage equal to three times the spell level of the interrupted spell. This damage cannot be avoided or transferred.
So, you cast Counterspell using a 4th-level slot against a 4th-level spell, and you take 8 psychic damage. If the spell you interrupted was 5th-level or higher, you could take 15 psychic damage or more!
Just a thought... *shrug*