Swordmage Feature Aegis of Ensnarement

You create an arcane link between yourself and a foe, allowing you to ensnare that creature.

At-Will        Arcane, Teleportation
Minor Action      Close burst 2

Target: One creature in the burst

Effect: You mark the target. The target remains marked until you use this power against another target. If you mark another creature using other powers, the target is still marked.
Until the mark ends, if the target makes any attack that does not include you as a target, it takes a -2 penalty to the attack roll.
If a target marked by this power is within 10 squares of you when it hits with an attack that does not include you as a target, you can use an immediate reaction after the target’s entire attack is resolved to teleport the target to any space adjacent to you. In addition, the target grants combat advantage to all creatures until the end of your next turn. If no unoccupied space exists adjacent to you, you can’t use this immediate reaction, and the target doesn’t grant combat advantage as a result of this effect.

Published in Arcane Power, page(s) 50, Player's Handbook 3, page(s) 152.