Thunder crashes around you as your skin becomes the dark blue-gray of thunderclouds and your eyes flash with lightning.

Daily   ✦     Lightning, Polymorph, Primal
Minor Action      Personal

Effect: You assume the guardian form of storm's wrath until the end of the encounter. While you are in this form, any enemy that starts its turn adjacent to you is marked until the end of your next turn and takes lightning damage equal to your Constitution modifier if you are able to take actions. In addition, at the start of each of your turns, choose one enemy that you can see within 3 squares of you. That enemy takes lightning damage equal to 5 + your Constitution modifier.

Published in Player's Handbook 2, page(s) 168.