Gory slash
rogue attack 25
Melee weapon
Requirement: wielding a light blade.
Target: one creature
Attack: Dexterity vs. AC
Hit: "4[W] + Dexterity modifier damage, and the target takes ongoing 10 damage and is immobilized (save ends both)."
Miss: "Half damage, and ongoing 5 damage (save ends). The target is immobilized until the start of your next turn."[MP:85]
Gory slash is a daily power available to rogues at 25th level.