Incantatrix

Incantatrix is a special prestige class on Faerûn

Incantrarixes are the most skilled practitioners of metamagic. They can shape spells in their raw effects and can modify the spells of allies, magic items and even active spells casted by another. They dislike extraplanar intrusions on Faerûn, so they actively seek and destroy the planar portals. Someone seems to think that they are now dangerous against normal opponents, but they change their mind as soon as they see the sheer distructive power of some spells modified by a couple of metamagic effects.

Note: most incantatrixes are female, but male spellcasters of this prestige class exist, too. They are called incantatars