Here’s the scenario:
A party member wants to fool an enemy into thinking that they are casting a spell. They take out components, do hand gestures, and starting chanting but do not actually initiate the casting of any spell. The enemy, fooled by this, casts counterspell at the pretend-spellcaster. How does this resolve?
Is counterspell successfully cast (obviously with no effect)? If so, is the slot used to cast counterspell lost?
Or, can counterspell not be initiated in the first place (since there is no real spell being cast)?
Xanathar's Guide to Everything (p. 86) addresses this issue in the section "Invalid Spell Targets":
If you cast a spell on someone or something that can’t be affected by the spell, nothing happens to that target, but if you used a spell slot to cast the spell, the slot is still expended. If the spell normally has no effect on a target that succeeds on a saving throw, the invalid target appears to have succeeded on its saving throw, even though it didn’t attempt one (giving no hint that the creature is in fact an invalid target). Otherwise, you perceive that the spell did nothing to the target.
Thus, you waste the spell slot used to cast counterspell. In fact, because nothing happened, the spellcaster might believe that they had successfully counterspelled a spell...
Correct answer by Icyfire on December 5, 2020
The spell whiffs, which is to say, it does nothing. In addition, you do spend the spell slot despite there being no countered spell, because you spent the effort and magic to cast the counterspell. I will say, because it relates to the question - one should generally be sure that there actually is a spell being cast beforehand. So, especially if the caster is trying to decieve them into wasting a counterspell, the DM should probably have the player make an arcana check to figure out whether or not it's a real spell before they cast it. Also, counterspell generally doesn't work on effects which have already been cast on a creature - that's what the dispel magic spell is for.
Answered by Matt D on December 5, 2020
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