How to do Counterspelling?

[wrecan]

Get it away from keywords. Keep it simple.

Counterspell Level XX Wizard Spell
Daily * Arcane, Implement
Action: Immediate Interrupt
Range: Ranged 10
Trigger: You are the target of, or within the burst or blast of, a power that does not have the weapon keyword, and does not have a range of "melee".
Attack: Intelligence vs. Fortitude
Target: The creature invoking the triggering power
Effect: The target does not attack, but the power is treated as if it had been invoked, for purposes of frequency (at-will, rechargeable, encounter, etc.)
Special: If the triggering power has a frequency other than at-will, the attack is made at a penalty of -2.

Sure, the wizard can counter things that couldn't be countered in prior editions, like a dragon's breath. But so what? Isn't that a form of magic as well?

 

[wrecan]

An alternate way to do it, which also resembles prior editions would be to make it a class feature.

Counterspell
You use your magic to attack, not your opponent, but his magic
Immediate Interrupt
Trigger: You are the target of, or within the burst or blast of, a power that does not have the weapon keyword, and does not have a range of "melee".
Target: The creature invoking the power.
Effect: Choose a spell you have memorized that makes an attack roll. Attack only the target with that spell. (The target must be in range of the spell.) If you hit, the target's own attack is disrupted, but you impose no other effects of your spell. You incur a penalty to the attack roll of -1 for each five levels difference between the level of the target and the level of the spell you invoked. On a hit, the triggering power has no effect.

This obviates the need for tracking dailies. You convert your own spells into a counterspell. Due to the penalty, you are unlikely to use your low level spells, but you might choose to in a pinch.