Is Counterspell overpowered? The answer is probably yes. Using just a reaction (ie. you can still use your own action to cast another spell or attack!), and a third level spell slot (minimum), you can negate the effect of any spell of 3rd level or lower cast within 60ft of you, and you have a decent chance of bringing higher level spells to a grinding halt as well.
During a recent encounter our poor Dungeon Master grew quite frustrated as the sorcerer in our party rendered a high level cleric powerless, by negating a succession of dangerous spells that would have put the combat right in the balance, all with just a couple of 3rd level spell slots. Maybe that’s why DM David voted it one of the four most annoying spells in D&D!
As a Dungeon Master the spell carries a double annoyance. It can make it harder to judge how tough to make encounters (if Fire Storm takes effect the party is going to be in a lot of trouble… if it doesn’t it could turn into a cakewalk), and from a story point of view it can replace epic happenings with the empty hiss of arcane magic fizzling out into nothing.
Of course you could simply ban the spell from the table, but that can feel pretty rough on those who consider it a key weapon in their armoury, so let’s look at some ways you can legitimately prevent it from getting overpowered without changing the existing rules.
1. Perception Check
The caster of Counterspell has to be able to see the caster of the spell they are trying to interrupt. But let’s remember that they don’t get a little notification in their inbox saying “someone within 60ft of you is trying to cast a spell, would you like to try and counter it?” Just because it’s possible for character A. to see character B., ie. there is a clear line of sight, doesn’t mean that character A. was looking in that direction at exactly the right moment. Unless the character in question was unquestionably focused on the caster have them roll a Perception check to see if they notice what the hell is going on. On a chaotic battlefield with multiple casters I’d recommend a DC of around 15.
2. Otherwise Engaged
I think it’s very fair to argue that even if the potential Counterspeller (as I will refer to them) can see a creature casting a spell, if they themselves are locked into a separate melee, they are likely to be much too busy dodging that mean-looking ogre’s spiked club to stand any realistic chance of foiling spellcasting in another section of the battlefield. If however a character is adamant that their main mission is to counter a creature’s spell, whether some other minion is blocking their path or not, you could make them roll DC 12 spellcasting ability check to see if they can react to the situation or not.
3. Don’t Automatically Reveal What Spell Is Being Cast
If you know one or more of your players has Counterspell up their wizards’ sleeves, then be smart. Don’t declare what spell your NPC is casting. Simply inform your player(s) that they see a creature (if indeed they do see them… see points 1. and 2.) about to cast a spell, and have them roll an Arcana check DC15. If they pass they correctly guess the spell being cast, otherwise they have no idea and have to gamble whether or not to use their spell slot to try and counter the spell on what might just be a magic missile or cantrip. What’s more if the character has never seen the spell cast before give them disadvantage on their Arcana roll (if they have seen it plenty, or frequently cast it themselves, you should probably give them advantage). If you want to be really mean roll for them privately, behind your screen, and feed them misinformation when they fail their roll. This way they never know for sure, because even when they pass the check and you tell them the truth, they don’t know they passed the roll, so can’t be sure to trust their character’s assessment.
4. Make The Players Act Instantly
The uncertainty caused by point 3. will create a lot hesitation… snap your fingers, and if they haven’t decided tell them they’re too late! They just lost their reaction. Better luck next time. (That is if they survive the Lich’s Power Word Kill… mwah ha ha ha!).
5. Get The Rules Right
When the spell being cast is higher than the spell slot being used to interrupt it the Counterspeller must make a DC check of 10 plus the spell level. They can add their spellcasting ability but NOT their proficiency bonus. (I mention this because we got this wrong on our table and indeed our frustrated DM might have got off at least one more spell if we had this clearer! There is actually a skill called Improved Abjuration available to Wizards who follow the School of Abjuration who reach 10th level that enables them to add their proficiency bonuses to this roll [p.115 of the Player’s Handbook]… chances are your players don’t have that!).
6. One Reaction A Turn Max.
Remember the spell does take a reaction. And every character only gets one reaction a round. So if they’ve cast Shield already for example, or indeed another Counterspell, or used Uncanny Dodge to halve some damage (if they are multiclass Rogue), then they’re shit out of luck.
7. Fight Fire(ball Extinguisher) with Fire(ball Extinguisher)
One other very obvious way to fight the power of Counterspell is to arm all your NPCs casters with it as well – a particularly good tactic if you want to persuade magic using characters on your table to drop it from gameplay altogether, as you’ll soon see them get frustrated when their own spells fizzle out and the combat is decided by the fighters in the party. (Do note however, despite some DMs arguing that you can, you can’t Counterspell a Counterspell. Aside from the ridiculousness that would ensue, that would also involve casting two spells simultaneously, which is not only against the rules, but also against common sense. Additionally CS is so fast there’s no way you could react to it… most spells take several seconds to cast, CS takes a split second).
Hipster Rules Fix
If, after applying all these factors to your gameplay, you still feel that the spell is overpowered let me suggest the following rules fix. Instead of setting a DC, the CS caster must contest the original caster each using their spellcasting ability modifier. If one of them is using a higher spell slot than the other, they get +2 modifier per slot higher.
Eg. Gandalf is a wizard with Intelligence 18 (+4 spellcasting modifier) and seeing the dastardly Harry Potter (Intelligence 16, +3 modifier) preparing a nefarious incantation he successfully rolls Arcana to recognise it. It’s the level 7 Finger of Death spell! Gandalf uses his highest spell slot left, a level 6, to try to counter it. He rolls a 15, which becomes 19 with his spellcasting modifier. Harry rolls 13, plus his own spellcasting modifier of 3, and an additional plus 2 as his spell is one level higher than the slot being used to counter it. His total is 18 (a draw would result in the spell being cast). Gandalf succeeds in his counter… just.
In my rules fix there’s also no such thing as an automatic counter, so you should roll/contest if even if you are countering a spell using a higher spell slot, getting +2 on your roll per slot level higher you use. (Otherwise a higher level wizard would systematically destroy a lower one without a chance, which is against the spirit of D&D).
Personally I quite like Counterspell, probably because I currently play as a multi-class Fighter / Rogue / Wizard, and it gives me a chance at least to avoid seriously nasty spells of magic users before engaging them in melee, where I have the upper hand. As someone with a long history of failing saving throws I really enjoy getting a second chance to avoid some excruciatingly annoying effect that is going to take my character out of the game for the rest of the encounter…