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Thundering Burst
Swordmage Attack 27

You slam your sword into the ground and send a sonorous boom outward.

Target: Each creature in burst

Attack: Intelligence vs. Fortitude

Hit: 2[W] + Intelligence modifier thunder damage. If the target moves before the end of your next turn, it takes 2d8 + your Constitution modifier thunder damage.

Aegis of Ensnarement: The target is also slowed until the end of your next turn.

Thundering Burst is an encounter power available to swordmages at the 27th level.[AP:63]