Is this an ability you have to use before the spell is cast? Or is it meant to be activated in response to the spell?

Assuming the latter, my suggestion for the wording would be:

> : ~ deals 2 damage to the controller of target spell that's targeting ~, and 1 damage to each creature that player controls.

Or if you want it to trigger when the spell is cast, you could do:

> Whenever a player casts a spell targeting ~, you may pay . If you do, ~ deals 2 damage to that player and 1 damage to each creature that player controls.

Either kind of ability will usually work out as "hexproof as long as you have untapped", but that's fine if you want it.

noted