Word of Vulnerability
Bard Attack 17
You speak a word of power as you strike your foe, and the foe becomes vulnerable to your allies' attacks
Melee weapon
Target: One creature
Attack: Charisma vs. AC
Hit: 3[W] + Charisma modifier damage. Until the end of your next turn, each ally who hits the target and has combat advantage against it deals extra damage equal to you Charisma modifier.
Word of Vulnerability is an encounter power available to bards at 17th level.[PH2:75]