So, I’ve been fumbling along being silly, but luckily remembered the two-weapon combat rules at the last minute, hence I present no silly complicated rules idea for double-weapons.
Qualities: Double, Pierce 2, Vicious 1, Defensive
Hard Points: 2
Weapon quality: Double; a melee weapon with this quality basically has two ends with the same… business end. These weapons count as two identical weapons for purposes of being used in conjunction the two-weapon fighting rules.
A second blade (or whatever business end the weapon has) is attached to the opposite end of the weapon.
To apply this attachment oneself requires the parts and an Average Mechanics check.
Basic Modification: Weapon Quality (Double) Mod, Increase Encumbrance (+1) Mod.
Modification Options: Weapon Quality (Defensive) Mod.
Hard Point Cost: 1
Cost: 500 or weapon base cost; whichever is higher.
Rarity: 5 or same as weapon, whichever is higher.
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