Zehir's band of power

A small gold ring which is significantly heavier than you would expect. Once attuned the weight changes. Its now significantly lighter than it looks and a little tighter then it was when you put it on.

While wearing this ring you can expend 1 charge to empower a spell. The spell must be a damage dealing spell of 1st level or higher. It must also be a spell that requires a saving throw, and not a ranged or melee spell attack. 

After casting the spell, roll a skill check with your spell casting ability. The DC is 11 + the spells level. On a success the spell deals double damage. On a fail, the spell is consumed and has no effect.