Concussive Echo is a Encounter power available to Wizards at 7th level[AP]
Concussive Echo
Wizard Attack 7
A focused blast of thunder slams into your foe, and the energy of the blast is stored in your enemy's body. When it next attacks, that energy is released in a concussive burst.
Encounter ✦ arcane, charm, implement, thunder
Target: One Creature
Attack: Intelligence vs. Will
Hit: 2d6 + Intelligence modifier thunder damage. The first time the target makes an attack roll before the end of your next turn, it deals 5 thunder damage to itself and to each enemy within 3 squares of it.