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Blistering outburst
rogue attack 17

Requirement: wielding a light blade.

Target: each creature in burst you can see

Attack: Dexterity vs. Fortitude

Hit: "1[W] + Dexterity modifier damage, and the target takes a −2 penalty to attack rolls until the end of your next turn."[MP:82]

Blistering outburst is an encounter power available to rogues at 17th level.