Xanathar's Guide to Everything (p. 85) gives an optional rule if a character wants to identify a spell:

Sometimes a character wants to identify a spell that someone else is casting or that was already cast. To do so, a character can use their reaction to identify a spell as it's being cast, or they can use an action on their turn to identify a spell by its effect after it is cast.

If the character perceived the casting, the spell's effect, or both, the character can make an Intelligence (Arcana) check with the reaction or action. The DC equals 15 + the spell's level. If the spell is cast as a class spell and the character is a member of that class, the check is made with advantage. For example, if the spellcaster casts a spell as a cleric, another cleric has advantage on the check to identify the spell. Some spells aren't associated with any class when they're cast, such as when a monster uses its Innate Spellcasting trait.

I'm thinking of completely replacing the check with comparing the passive Arcana score and the DC (15 + spell level). This would also not require a reaction to perform.

However, I'm not sure whether this will be balanced or not. The goal is to allow identifying spell before casting counterspell. The side goal is to reduce dice rolling.

One of my main concern is early level this would be useless, as even with proficiency in Arcana, you would only get at most +5 (+3 from INT and +2 from proficiency). Except if you have expertise, you will never be able to identify even 1st level spell. Without expertise, you will only be able to identify up to 5th level (10 +5 INT and +5 proficiency against DC 20 for 5th level spell).

Is this modification (completely replacing identification using passive score instead of actively rolling Arcana) underpowered? Can it be remedied by changing the base DC to 10 instead of 15? What are some other concern I might have missed?

This rule will also apply on other situations other than for counterspell.

  • \$\begingroup\$ Are you only afraid of it being underpowered? You are effectively giving a free reaction, so maybe it would be worth to ask if it isn't overpowered at some point, too? \$\endgroup\$
    – Mołot
    Apr 2, 2019 at 8:41
  • \$\begingroup\$ @Mołot no, I only mention underpowered because I feel this is underpowered because of the reason stated. I might be wrong and this is actually way overpowered. If it is overpowered, I'd be gladly to read what's the reason and learn balancing homebrewed rules. \$\endgroup\$
    – Vylix
    Apr 2, 2019 at 8:47
  • \$\begingroup\$ What is the point of using your reaction to identify a spell as it's being cast? You still can't counterspell it, since reaction was already spent. \$\endgroup\$
    – enkryptor
    Apr 2, 2019 at 9:52

3 Answers 3


I use this, with DC = 10 + the spell's level

And I have used it since before I read the rules in XGtE with absolutely no problems at all and my group really appreciated it.

This is also exactly what passive checks are for. If you notice something your brain immediately makes the link to your knowledge and you just know, you don't need to stop and concentrate to know something, you either know it, or you don't.


This makes Counterspell more powerful than it seems to be intended in XGtE, but I think that rule sucks and having a spell countered, or countering a spell is more fun than wasting a counterspell. But then as a GM I am on the players side and like them being informed about anything and everything.

If using DC10 as the base drop the advantage rule, because that boils down to +5 and means you start on a base of 15 passively so pretty much recognise everything.

I did try DC = 15 + the spells level, and this has the effect of making non-arcane spells more difficult to counter. I didn't like this personally, but it can be a flavourful touch. The DC15 is essentially taking into account that you have advantage on your own type of spells. I think here it is a group preference thing.


I find that more information in the hands of the PCs is better than less information, and any clever use of a passive skill such as this is very much within my style of DMing, but each to their own and this is steering away from RAW.

  • \$\begingroup\$ "and this has the effect of making non-arcane spells more difficult to counter." - isn't this just as difficult, on average, as original rule in XGE? \$\endgroup\$
    – Mołot
    Apr 2, 2019 at 10:12
  • \$\begingroup\$ @Mołot I was referring to the comparison to DC10, but yes. The difference with XGtE would be action economy. \$\endgroup\$
    – SeriousBri
    Apr 2, 2019 at 10:27
  • \$\begingroup\$ I think this answer can be improved by explaining at the top explicitly what "this" is that you use. OP suggests multiple rules in their part and it's not clear exactly what rules you are agreeing with. \$\endgroup\$ Apr 2, 2019 at 12:00
  • \$\begingroup\$ Does this all mean that as a side effect if the spell level is outside their passive then they know it's above a certain level? They still gain information even when they fail, right? \$\endgroup\$
    – NotArch
    Apr 2, 2019 at 13:21
  • \$\begingroup\$ What is "this has the effect of making non-arcane spells more difficult to counter" supposed to mean? The Arcana skill is magic in general, not arcane magic specifically. Why would the source of the spell matter? \$\endgroup\$
    – T.J.L.
    Apr 2, 2019 at 13:37

Passive arcana checks greatly increases the power of counterspell and removes a layer of strategy from wizard battles.

Information is power. Knowing what spell is being cast without having to spend encounter resources (a reaction) is powerful. The uncertainty of if counterspell will be wasted is one of it's drawbacks. Mitigating this drawback makes counterspell much more powerful by making choosing the optimal counterspell strategy much easier.

Uncertainty and spell casting game theory

When both sides are aware of counterspell and it's cost, choosing when to use it involves a fair bit of strategy. Like a battle of wits. Consider the interesting case of two opposing sides that both have wizards. Choosing when to use counterspell includes thinking about:

  • What is the chance that the opponent actually has counterspell in their current repertoire?

  • Is the opponent the sort of wizard that leads with their most powerful spells?

  • Is the opponent the sort that knows about counterspell and uses low level chaff to draw out the counter?

Given limited uses of counterspell and variable chances of success, what's the best strategy to choose when to use counterspell? Giving passive information about what spell is being cast makes discerning when to use it far less involved.

Making counterspell a tactical aspect of NPCs personality in the campaign

Generally before an encounter begins, choose and write down the strategy of the NPCs or monsters. Stick to that to avoid opponents being proxies of the DM's knowledge. This makes the NPC behave according to a model that isn't what the DM knows or thinks is best at the time. E.g. Rory the opponent wizard uses his most powerful spell first when threatened, and assumes his enemies do the same. So he counterspells the first spell cast against him.


No hint is too obvious when giving players information about opponents. If there is a wizard they're coming up against, it's likely other people know about them. Give clues about their personality. Some stories or anecdotes might be useful;

  • "Rory's quick to overreact. One time saw 'em summon a sledge hammer to squish a fly."
  • "Rory doesn't like to let anyone else cast spells. Counters the first one right off the bat to shut other wizards down... well, before he cooks them with a fireball."

With the above information, the players could successfully deduce the strategy of Rory and design their strategy to match. E.g. lead with magic missile to draw his counter spells out and counter his first couple of spells. Then use more powerful spells to defeat the encounter.

The power of teamwork is a win win.

Another way a party can make their counterspells more powerful is by teamwork. Having an arcana proficient companion can greatly increase the efficacy of a wizard and give a non-wizard an opportunity to participate in the magic side of an encounter.

In practice, a companion of a wizard can use their arcana ability to identify a spell as it's being cast to shout in order to inform the wizard to use their reaction to cast counterspell. In this way, the Arcana skill can be used to facilitate when to know when to counter a spell being cast. The wizard is trusting the companion to make a judgement call and decide to should "counter it!", while the companion is trusting their wizard to rely on their judgement of what should be countered.

In this way, the drawback of counterspell (not knowing) is mitigated by teamwork between players. This method is a game mechanics win and a group role play win.


It makes Counterspell too powerful

Under the current rules you can either identify it or Counterspell because both use your singular Reaction.

Most simply explained with an example:

Current Rule

DM: “The lich is casting a spell.”

Me: (Internal monologue) Jeez, it’s a lich, those guys know Power Word, Kill and I don’t want that coming my way. Do I use Counterspell? Best to be safe. But at what level? To be sure I have to use my only 9th level slot. But what if he’s going for a 5th level AoE? Then I’ve wasted my slot and he can Power Word, Kill next turn. What to do?

DM: Are you going to do something?

Me: Yeah. Counterspell at 5th level.

Your rule

DM: “The lich is casting Ice Storm.”

Me: Counterspell at 5th level.

Where’s the fun in that?

  • 1
    \$\begingroup\$ Where is the fun in wasting a 5th level slot against Power Word Kill if Counterspell in a 3rd level slot would have the same chance of countering it? This is the opposite of what I would call fun. \$\endgroup\$
    – András
    Apr 2, 2019 at 8:14
  • 10
    \$\begingroup\$ Explaining changes in action economy etc would be far more useful than opinion about totally relative feeling of fun. \$\endgroup\$
    – Mołot
    Apr 2, 2019 at 8:15
  • 1
    \$\begingroup\$ "Me: (Internal monologue)" That can take a large amount of time, the proposed rule greatly increases the pace of the fight. \$\endgroup\$ Apr 2, 2019 at 8:16
  • 5
    \$\begingroup\$ I think counterspell is nerfed into oblivion by the XGtE rule which is an amazing book, but the spell identification rule is by far the worst imho. \$\endgroup\$
    – SeriousBri
    Apr 2, 2019 at 9:49
  • 2
    \$\begingroup\$ @Mołot I’m perfectly happy with your comment and your vote. Please take mine at face value - your comment is the start of a good answer. \$\endgroup\$
    – Dale M
    Apr 2, 2019 at 12:10

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