Double weapons share the following traits.
• You must wield a double weapon in two hands to use it.
• A Small character cannot wield a double weapon unless the weapon has the small property.
• Wielding a double weapon is like wielding a weapon in each hand. In the table, the first line of the double weapon’s entry describes the end of the weapon wielded in your main hand. The indented line describes the weapon’s other end, wielded in your off-hand. The two ends of a double weapon can have different proficiency bonuses, damage, properties, and weapon groups. The weight and price entries represent the total for the weapon, rather than only one side.
• When adding an enchantment that requires a particular weapon type, at least one end of the weapon must match the requirement. For example, an urgrosh could gain the vorpal enchantment, even though only one end meets the requirement of “heavy blade or axe.”
• An enchanted double weapon gains all benefits of the enchantment on each end (even if one end would not normally qualify for the enchantment). This does not increase the frequency of use of any power possessed by the item; if you wield a double weapon with a daily power you can still only activate that power once per day.
Published in Adventurer's Vault, page(s) 10.