One of your blades finds your foe, then your other one does so. You cap the attacks by scissoring the foe with both weapons

Encounter   ✦     Martial, Weapon
Standard Action      Melee weapon

Requirement: You must be wielding two melee weapons

Target: One creature

Primary Attack: Strength vs. AC (main weapon)

Hit: 2[W] + Strength modifier damage

Effect: Make a secondary attack against the target

  Secondary Attack: Strength vs. AC (off-hand weapon)

  Hit: 1[W] + Strength modifier damage. If the primary attack also hit, the target takes 5 + your Strength modifier extra damage

Published in Dragon Magazine 377, page(s) 72.