Here's one that my DM and I can't seem to see eye-to-eye on:
Spells that have a duration of 'instantaneous' cannot be dispelled with Dispel Magic. No problem, makes sense that once that fireball goes off, it's gone, you can't dispel it later in the round. But what about counterspelling it? If you don't have fireball memorized can't you use dispel magic to counterspell it as outlined in the rules? Things are a bit fuzzy in the text:
Pg 209
Dispel Magic as a Counterspell: You can usually use dispel
magic to counterspell another spell being cast without
needing to identify the spell being cast. Dispel magic doesn’t
always work as a counterspell (see the spell description).
Pg 273
Some spells, as detailed in their descriptions, can’t be defeated by dispel magic...The effect of a spell with an instantaneous duration can’t be dispelled, because the magical effect is already over before the dispel magic can take effect.
Counterspell: When dispel magic is used in this way, the spell
targets a spellcaster and is cast as a counterspell. Unlike a true
counterspell, however, dispel magic may not work; you must make a
dispel check to counter the other spellcaster’s spell.
Now, I believe that you can counterspell any spell regardless of it's duration with Dispel Magic as long as you make the dispel check. My DM is stuck on the 'can't be defeated by Dispel Magic' bit. I think there are two distinct uses of the Dispel Magic spell here: the main one, usable to dispel an on-going spell effect (such as bull's strength) that had previously been cast, and the secondary one, counterspelling a spell as it is being cast. In the second case, the Dispel Magic spell targets the spellcaster and 'grounds out' their magic as they are casting it, or as a party member put it, it powers the counterspell. I don't see an imbalance to my interpretation, as using Dispel Magic blows a level 5 spell slot, regardless of what the enemy caster is casting (woo hoo, I blocked that cantrip...), and if I blow the dispel check it's all for naught, whereas the regular counterspell is 100% effective and only uses a spell slot of the same (relative) level.
Thoughts?