Haunting spirits
shaman attack 1
Target: one creature
Attack: Wisdom vs. Will
Hit: "1d6 + Wisdom modifier psychic damage. Until the end of your next turn, the target grants combat advantage to an ally of your choice."
Level 21: "2d6 + Wisdom modifier psychic damage."[PH2:121]
Haunting spirits is an at-will power available to shamans at 1st level.