The basic rules from the SRDs, which we have not significantly changed, are that to fight with two weapons, you must have either two mêlée weapons (e.g., a club and a knife) or two one-handed ranged weapons (e.g., two pistols). When you wield two weapons, you get a single bonus attack with your off-hand. You can mitigate those penalties with two feats: Over-Sized Weapons, which effectively renders your off-hand weapon “light,” and Two-Weapon Fighting, which simply reduces the penalty.
|primary hand||off hand(s)|
|off-hand weapon is not “light”||-6 to attack||-10 to attack|
|off-hand weapon is “light”||-4 to attack||-8 to attack|
|Two-Weapon Fighting feat||-4 to attack||-4 to attack|
|Two-Weapon Fighting feat and off-hand weapon is “light”||-2 to attack||-2 to attack|
In order to gain additional off-hand attacks, you have two options. First, you can take the Improved Two-Weapon Fighting feat, which grants an additional iterative attack with your off-hand. You can take Improved Two-Weapon Fighting multiple times to gain additional iterative attacks with your off-hand as part of a full-attack action. Basically, this means that you can take a full-attack action with your off-hand, but you have to “buy” your individual, off-hand attacks with the Improved Two-Weapon Fighting feat.
Second, you can take the trait Appendages (and the appropriate enhancements) and build yourself an additional off-hand. You can then apply Two-Weapon Fighting to each one of your off-hands, following exactly the same rules as above. At that point, “two” weapon fighting is a euphemism; it’s really Multi-Weapon Fighting.
Once you have set up all of your options, please calculate your attack bonuses before the game starts. It’s just plain impolite to do all that math at the table.
Note that these two-weapon fighting rules integrate without modification into the Full Flurry System.