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Flickering venom
warlock (dark) attack 1

ranged 5
Dark Pact: ranged 10 instead of 5

Target: one creature

Attack: Charisma vs. Reflex

Hit: "2d8 + Charisma modifier force damage, and if you have combat advantage against the target, you also deal poison damage equal to your Intelligence modifier."[FRPG:35]

Flickering venom is an encounter power available to warlocks at 1st level.