If you are a spellcaster capable of coun tering a spell on your own, you can also access the ring's secondary ability. Once per day as an immediate action, you can attempt to counter a single spell cast by a spellcaster you can see, provided he is within 100 feet. Like the ring's other ability, this one requires no preparation or knowledge on your part. You need not make a Spellcraft check to identify the spell being cast, and the spell you use to counterspell can be of any level. This counterspell attempt functions like greater dispel magic used to counter a spell, except that you add your caster level to the coun terspell check (maximum +20).