Minor action to use Promise of Storm, gaining +1 to attack rolls and +2d8+6 to damage with thunder/lightning powers UEMNT.
Standard action to use Ice Storm, converting to lightning per her paragon path, unfriendly area burst 3 centered at L19.
Int (implement) vs. Fort, and I'm guessing she has CA since they presumably can't see her.
Robed cultist1: (1d20+20)
And if he's still there, High cultist: (1d20+20)
lightning damage and the target is immobilized (save ends).
Miss: half damage and the target is slowed (save ends).
Effect: the burst creates a zone of difficult terrain that lasts until the end of the encounter.
Move action to shift 1 square to the left