[Zeldor]

If there are 5 ones new one targets random one [assuming there isn't the same one on in play]. And you get a cost comparison. I think +5 gems for every caster level above required [when casting, not when dispeling], boosters don't give that bonus [though don't give the penalty if caster was below] + random roll [you'd have to check manual, use search option to see what is the roll] + additional gems spent.