You mark an area in your mind and feed arrows into it every time you have a spare moment.

Daily   ✦     Martial, Weapon
Standard Action      Area burst 1 within 20

Requirement: You must be wielding a bow or a crossbow.

Target: Each creature in the burst

Attack: Dexterity vs. AC

Hit: 1[W] + Dexterity modifier damage.

Effect: Until the end of the encounter, when a creature moves into the area, you can make a ranged basic attack with a weapon against that creature as an opportunity action. You can move the affected area up to 3 squares with a move action.

Published in Dragon Magazine 383, page(s) 50.