Might of Mystra

If a priest casts a might of Mystra spell before a friendly or hostile wizard casts another spell, the might allows the priest to precisely duplicate the effects of that one spell. No material components are required for the priest's magic and the priest need not even know the name or nature (school) of the spell to be copied, but he must have witnessed either its casting or its results. The decision to copy a spell must be made the round after it is witnessed or the ability to use might of Mystra to copy that one spell is lost. Once might of Mystra is used to copy a spell, it ends; otherwise, it ends after one day has passed.

The priest's spell deals exactly the same points of damage, affects the same volume of area (if applicable), and lasts for exactly the same duration, as the spell being copied. However, the priest casting the might of Mystra spell can select a different target or area of effect and both target creatures and items affected by the magic are allowed new saving throws against the priest's spell as if it was a new casting of the same spell the priest copies.