Twin Strike Feat

You have mastered the art of distracting your opponent with two weapons before closing in for a deadly blow. You gain the following benefits:

Prerequisite: None

• Increased Damage. When you engage in two-weapon fighting, you can add your ability modifier to the damage of the extra attack.
• Double Strike. When you engage in two-weapon fighting, as long as the weapons' damage dice are d8 or smaller, you may choose to attack with both weapons simultaneously. Before rolling an attack, you may choose to take a -3 penalty to the attack roll. If the attack hits, you roll damage dice for both weapons, only adding your ability modifier once.
• Riposte. When you are wielding two weapons and an opponent misses a melee attack against you, you may use your reaction to make one melee attack with one of your weapons.

Source: KCLL, page 277

Note: Doubling Up

• It is intended that on-hit effects intrinsic to the weapon work with Twin Strike - if your GM lets you have two flameongue short swords, that's on them. But spells that apply on-hit effects (e.g. holy weapon, hunter's mark) only apply once per attack.