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Felling gash
rogue attack 23

Requirement: wielding a light blade.

Target: one creature

Attack: Dexterity vs. Reflex

Hit: "4[W] + Dexterity modifier damage, and you knock the target prone."
Ruthless Ruffian: The target is also dazed until the end of your next turn.[MP:85]

Felling gash is an encounter power available to rogues at 23th level.