Polearm Gamble

Paragon Tier
Prerequisite: 11th level, Str 15, Wis 15
Benefit: When a nonadjacent enemy enters a square adjacent to you, you can make an opportunity attack with a polearm against that enemy, but you grant combat advantage to that enemy until the end of the enemy’s turn.
Special: Weapon feat

Published in Player's Handbook, page(s) 204.