[RPG] Can one use Witch Bolt to prevent spell casting

concentrationcounterspellingdnd-5esaving-throw

Witch bolt seems to have a bad rap. One difference I see between witch bolt and other spells is that it is sustained/continued/ongoing damage.

If I spam a spell caster with fire bolts, magic missiles or even fireball, there's still a gap between the time I deal damage, and the next time I deal damage, which could conceivably give an opposing spellcaster a chance to cast their own spell without a concentration check.

If I use witch bolt on a spell caster, won't this require them to make a concentration check automatically in order to cast a spell? That seems like a pretty nasty way of dealing with a spellcaster (who may not have a very high constitution). Even 1 HP of damage would require a DC 10 constitution saving throw, right?

Too bad you can't upcast it to cause higher damage in later rounds. (Even one round per level – a second level spell slot also causes the extra damage in the second round, etc.)

Best Answer

You only make a concentration check when you take damage.

The rules for concentration state:

Whenever you take damage while you are concentrating on a spell, you must make a Constitution saving throw to maintain your concentration.

Witch bolt states:

on each of your turns for the duration, you can use your action to deal 1d12 lightning damage to the target automatically.

Witch bolt can only deal damage on your turn, so a target would only have to make a concentration check on your turn when you use your action to trigger witch bolt. Additionally, there are no circumstances where a concentration check is required for casting a spell with a casting time of 1 Action or Bonus Action.

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