Prevent monster heal, can merc apply

[Wyrm]

None of the Sorc skills are attacks, unless you count hitting a monster with a weapon that's been Enchanted.

An easy way to think of what an attack (that adeyke refers to) is, is that it's any attack that uses your weapon to deal damage. For example, when you throw a Plaugue Javelin, the javelin that hits monsters is an attack, but the poison cloud that spreads from it isn't.