With cover or concealment at initiative check, make a Stealth check to become hidden.
Use fade away as an encounter power.
Your origin is fey, not natural
Use ghost sound as minor action, 1/encounter.
Eyebite spell, Misty Step boon: When cursed foe is dropped to 0 hp, you can teleport 3 squares (free).
If no allies are closer to target than you, get +1 on ranged attacks against the target.
On your turn, if you move 3+ squares from starting square, gain concealment until end of your next turn.
Once per turn (minor), curse nearest foe you can see; deal extra damage to cursed foes.