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Surprising assault
rogue attack 17

Requirement: wielding a crossbow, a light blade, or a sling.

Target: one creature

Attack: Dexterity vs. AC

Hit: "2[W] + Dexterity modifier damage, and the target is dazed until the end of your next turn."
Cunning Sneak: The target is stunned instead of dazed if you were hidden from the target when you made the attack.[MP2:67]

Surprising assault is an encounter power available to rogues at 17th level.