Skills for an Inferno hero.

Here is a description from a fan-made guide:

Counterspell.
A special combat skill that negates any effects of the opponent's next spell, but consumes twice as much mana as the spell required.

However, a problem arises if the enemy has the "Spellcraft" skill, because the counterspell is a combat skill, and our "Spellcraft" skill does not affect it. The enemy, having "Spellcraft," will constantly skip one cast, apply one, and so on. But if you combine it with "Empathy" in the leadership branch, the opponent will behave completely differently.