[@Archangel89]

Narberal is a level 63 character capable of casting Chain Dragon Lightning, which is apparently a 7th level spell. She has levels in Fighter (1), War Wizard (10), Elementalist: Air (10), Armored Mage (10), and 31 other miscellaneous classes, plus 1 Racial level in Doppelganger. As Irish said, it probably helps if you have levels in primary caster classes.