Can a Lore bard use Cutting Words against the attack roll/ability check of a sorcerer's Subtle spell?

Question

Imagine the following situation: a College of Lore bard is battling against a sorcerer who has learned the Subtle Spell metamagic option.

The Lore Bard goes first and casts a high-level spell, which the sorcerer attempts to Subtle counterspell with a lower level spell slot.

Since counterspell only has a somatic component and the Subtle Spell metamagic option removes that, the counterspell is not detectable by the Lore bard. The sorcerer also has to roll an ability check (as part of counterspell) in order to successfully counter the bard’s spell.

However, could the Lore bard still use his Cutting Words feature to remove a Bardic Inspiration die on the sorcerer’s counterspell ability check, even though the Bard does not know that a spell is being cast?

The same question also applies to other spells with only verbal/somatic components (which can be Subtle Spelled) that include an attack roll or ability check to function, such as dispel magic or chaos bolt.

Answer 1

Yes, you can use Cutting Words even against a spell with Subtle Spell used on it

Counterspell's trigger is:

when you see a creature within 60 feet of you casting a spell

If used, the sorcerer's Subtle Spell metamagic option effectively makes it impossible to perceive the casting of a spell with only somatic and verbal components - and thus impossible to counterspell.

Unlike counterspell, however, the College of Lore bard's Cutting Words feature doesn't require seeing a creature "casting a spell. The feature description states:

When a creature that you can see within 60 feet of you makes an attack roll, an ability check, or a damage roll, you can use your reaction to expend one of your uses of Bardic Inspiration, rolling a Bardic Inspiration die and subtracting the number rolled from the creature’s roll.

Cutting Words doesn't rely on you seeing someone "casting a spell". It doesn't even rely on you seeing someone "making an attack roll/ability check/damage roll", because those are simply mechanical abstractions of what's actually happening in-universe. The primary things it requires are that you see the creature and that it be within 60 feet of you.

As a result, you can basically attempt to use Cutting Words on the attack or damage roll or ability check of any creature you see within 60 feet.

Of course, your DM may houserule that you need to be able to visibly perceive that the creature is doing something in order to react to it, but that's just up to your DM (and the players).

Answer 2

Yes, a Lore bard can use Cutting Words to affect an ability check occasioned by a Subtle spell.

Implicit in your question, I think, is an assertion: the Cutting Words ability ought to require the ability to see and recognize that the target is doing something. Since a Subtle casting of counterspell wouldn't be detectable -- so the argument would go -- it ought not trigger the ability. Given the description of the ability as using words to distract and confuse others, PHB p. 54, that argument is perhaps understandable... but it's nevertheless incorrect.

Remember this beacon of guidance for interpreting 5e:

Beware of claims that a rule does something mentioned nowhere in that rule or elsewhere in the core books. There aren't secret rules.

Cutting Words doesn't require recognizing that something is happening to trigger the ability. Its trigger is merely:

When a creature that you can see within 60 feet of you makes an attack roll, an ability check, or a damage roll...

Think of it as reflexive: one of the enumerated events happens, and you get to react to it, period. You do need to be able to see your target, but that's it. If the designers had intended some further requirement, they would've said so.