[RPG] Can a concentration spell be cast without actually concentrating on it for an “instant” effect

concentrationdnd-5espellcasting

The book says:

Concentration. Some spells require you to maintain concentration in order to keep
their magic active. If you lose concentration, such a spell ends.

So what happens if, for example, you are already concentrating on a spell, and cast Witch Bolt without concentrating. Would you get the initial arc of blue energy, or would it not even go off?

I am asking if you can cast a spell that says concentration without concentrating for an immediate effect. This would be useful to avoid interrupting your existing concentration. In essence, if you are concentrating on thing A (doesn't have to be a spell since other things need concentration), can you cast a concentration spell getting an immediate effect without losing concentration on thing A?

Since the definition of concentration is to keep the spell active (meaning it is already active) I would think that you would get the initial effect (if it had one) without the need to concentrate on it.

Best Answer

No. Casting a concentration spell immediately breaks any existing concentration.

One of the rules clarifications in Xanathar's Guide to Everything (pg. 5) addresses this issue directly:

As soon as you start casting a spell or using a special ability that requires concentration, your concentration on another effect ends instantly.