[RPG] Can a Spell cast with Subtle Spell and an Arcane Focus be Counterspelled


Recently, this question asked whether you could Counterspell a spell without a material component that completely eliminates component requirement via Subtle Spell. The answer was no, with a Crawford Tweet as evidence. The following was asked in response to the Tweet but never answered and is a situation likely to occur in a campaign I'm running:

A Sorcerer uses Subtle Spell on a no-cost material component spell like Sleep or Fireball which they cast with a small crystal Arcane Focus kept tightly gripped and hidden in their fist.

In previous editions, spell descriptions indicated how materials were to be used: sprinkling sand or rose petals for Sleep, or throwing a ball of bat guano for Fireball. 5e doesn't provide these, nor does it seem likely such usages are possible with a Spellcasting Focus.

So, in this situation, is there enough information for another spellcaster to realise a spell is being cast for them to Counterspell?

Best Answer

If you follow Xanathar's Optional rules,

Yes, the spell could still be countered.

From XGtE, p. 85, "Perceiving a Caster at Work":

To be perceptible, the casting of a spell must involve a verbal, somatic, or material component. The form of a material component doesn’t matter for the purposes of perception, whether it’s an object specified in the spell’s description, a component pouch, or a spellcasting focus.

It's irrelevant whether the Arcane Focus is small or not, casting a spell with it makes it perceptible. The only way to make casting imperceptible is to remove the Material, Somatic and Verbal components. From XGtE, same section:

If the need for a spell’s components has been removed by a special ability, such as the sorcerer’s Subtle Spell feature or the Innate Spellcasting trait possessed by many creatures, the casting of the spell is imperceptible.

As far as I know, there is no other way to make the casting of a spell imperceptible (aside from being invisible or similar). As long as it has a spell component, it is perceivable, and thus, can be countered. Even if the spell has no components at all, it can be obvious you have cast a spell! Some spells have flashy descriptions. In Fireball, for example,

A bright streak flashes from your pointing finger to a point you choose within range

So a Subtle Sorcerer with Greater Invisibility can cast it without being perceived, but everyone will see the streak of light coming from his position. It won't be countered, but everyone will know there was a trigger happy pyromaniac around.

That being said, the DM is free to make calls where common sense applies. If an enemy is really far, if there are lots of obstacles in between (like a crowd), if the perceiver is blind, etc, all of these should be taken into account. At my table, for example, our Totem of the Eagle Barbarian can spot spells being cast from a mile away, other players cannot.

However, the rules address the OP's specific example, of using a "small Arcane Focus", and because "the form of a material component doesn’t matter for the purposes of perception", you could just as well be waving around a giant Gandalf quarterstaff.