When using Dispel Magic as a counterspell, does it have to be a prepared action?

[timoteo]

I ran into this tonight during a session, and I thought because Dispel Magic had an instantaneous effect that it negated the need to prepare an action, like you normally would with a normal counter-spell. DM said I had to have prepared the action, but then I don't see why you wouldn't just prepare an attack or offensive spell in that case. Can someone clarify this for me? (I've used Dispel Magic before, but not as a counterspell, so a little confused here.)

Thanks!

[Mr Adventurer]

Your DM is right.

You might use it when you want to counterspell but you don't have the right spell prepared.

You might want to counterspell when the enemy mage has defences that make your attack spells unlikely to succeed.

[NontheistCleric]

Dispel Magic's casting time is still 1 standard action, so unless you are holding an action ready, you wouldn't be able to cast Dispel Magic in response to an opponent's spell, as standard actions, if not readied in response to some particular circumstance, can only be taken within your turn, not the enemy's. Of course you could, instead of readying a Dispel Magic in response to enemy spellcasting, instead ready an action to cast an offensive spell in response to enemy spellcasting. But that offensive spell could not be used to counterspell the enemy spell unless


It was the same spell (or of the same school if you had Improved Counterspell)
It was a spell that specifically countered the enemy spell
..and you correctly identified the spell the enemy was casting so that you could respond to it using one of the above methods


In any case, though, you need to ready an action to counterspell, whether you are doing it with a specific offensive spell matched to the enemy spell or Dispel Magic, that does not need to be matched to the enemy spell. You could also ready an action to simply cast an offensive spell when the enemy casts, but that would not result in a counterspell, only an exchange of offensive magic.

The exception to this is when you have an ability like Divine Defiance, which allows you to counterspell as an immediate action (which can be taken out of turn whenever you want), so you don't need to ready an action, although you would need to have a turn undead attempt to power the feat.

[timoteo]

Yeah, I just recently realized I was confusing immediate with immediate action ... duh. Not sure what I was thinking. But thanks to you both for the other points ... good ideas all around.

Take care.