Reflect

A more dangerous variant of Counterspell. Reflect takes your spell, and treats it as if the enemy cast it on you instead. Not only do you lose mana from the cast, but you are subject to whatever negative effect the spell would have. This means that if a rain is reflected, you and those around you will be hit by the rain, or if a Lifetap is reflected, you'll lose hp, and the enemy will gain some. Only known way around is using PBaoes, which cannot be reflected or counterspelled.

Like counterspell, Reflect has a cooldown, though sometimes very small, that one can land spells during. Other than high resists, there is no way to avoid the effects of Reflect.