You create small pockets of chaos to warp the energy of your next spell around your allies.

Encounter   ✦     Arcane
Minor Action      Close burst 10

Effect: Choose a number of squares in the burst equal to your Dexterity modifier. Until the end of your turn, any creature whose space is entirely in those squares is not affected by your area or close arcane powers.

Published in Player's Handbook 2, page(s) 144.