D&D4 Wiki
Snake Strike
Swordmage Attack 17

Your sword extends into the form of a shadowy asp and bites an enemy. If that foe dares to leave your side, poison assails it a second time.

Ranged 10

Target: One creature

Attack: Intelligence vs. Fortitude

Hit: 2d8 + Intelligence modifier poison damage. If the target ends its next turn in a space that is not adjacent to you, it takes 1d8 + your constitution modifier poison damage.

Snake Strike is an encounter power available to swordmages at the 17th level.[AP:59]