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Shade twin
warlock utility 2

Target: one creature within the area of effect

Effect: "You adopt the target's appearance until the end of your next turn. Creatures that observe you using this power are aware that you have done so. You gain a +5 power bonus to Bluff checks related to mimicking the target. Whenever you take damage while you have adopted the target's appearance, the target takes psychic damage equal to half the damage you take. Whenever the target takes damage from this effect, roll a d20. On a 10 or higher, the effect ends."

Sustain minor: "The effect persists until the end of your next turn."[HoS:67]

Shade twin is a daily power available to warlocks at 2nd level.