You can make as many off-hands attacks that you have off-hands available to attack. The Blade Boot add another off-hand attack (with the feet) to your pool of available attacks (just like the Barbazu Beard with the head).
The Two-Weapon Fighting and Multiweapon Fighting feats are a mess. They should work to reduce the penalty in making all off-hands attacks, but check with your DM to see that he does allow it. If not, then you will only have the primary hand and first off-hand attack which would have a reduced penalty.
The Light Walker rogue's talent would indeed compensate the drawback from fighting with a deployed Blade Boot.
And as always, the DM have the final word.
It seems that there is a lot of confusion going on…
To make this build possible, we need to answer the following questions :
- Is it possible to make more than one off-hand attacks in a round?
- Would the Two-Weapon Fighting feat work for more than one off-hand?
- What about the Multiweapon Fighting feat?
- Does the Blade Boot count as an extra off-hand weapon?
1) Is it possible to make more than one off-hand attacks in a round?
Yes, it is possible, but as much as you have off-hands available. Yet, there isn't any explicit rule on that. So how can we know that?
First, we have the Armor Spikes, the Tentacle and the Vestigial Arm Alchemist Discoveries. Each of them explicitly state that they can't be used to add another attack in the round, but can only be used to replace one that you already have.
You can’t also make an attack with armor spikes if you have already made an attack with another off-hand weapon
The tentacle does not give the alchemist any extra attacks or actions per round
The (Vestigial) arm does not give the alchemist any extra attacks or actions per round
Second, we have the Kasatha with the Multi-Armed trait which state that they have one primary hand and three off-hands. And be able to have two additional off-hands cost 8 Race Points… This drawback clearly show that having more than one off-hand is an advantage which need to be balanced.
A Kasatha has four arms. One hand is considered its primary hand; all others are considered off hands.
Third, in the normal description of the Multiweapon Fighting feat, it is specified that fighting with more than one off-hand work just like with only one.
A creature without this feat takes a –6 penalty on attacks made with its primary hand and a –10 penalty on attacks made with all of its off hands.
Fourth, just like for the Blade Boot, the Barbazu Beard explicitly say that you can use the part wearing it as an off-hand, and when clearly explain that it mean to have an extra off-hand! (thanks to @HeyICanChan for pointing me out this weapon)
A barbazu beard can be used as an off-hand weapon that requires no hands to use; thus, a warrior could combine use of a barbazu beard with a two-handed weapon.
Fifth, nowhere it is said that you can't make as many off-hands attacks than you have off-hands available… (-_-')
With all of that, we can conclude that indeed, you can make as many (un)armed off-hands attacks that you have off-hands available.
2) Would the Two-Weapon Fighting feat work with more than one off-hand?
Here the answer would be MEH…
Like @MikeQ said, the Two-Weapon fighting whole stuff is a mess…
First, why do we need the Two-Weapon Fighting feat? That's because we have a huge penalty in using more than one weapon in each hands to fight, as state in the Two-Weapon Fighting section from the combat entry. Meaning that yes, you can attack with multiple weapons, but you will probably miss… And the Two-Weapon Fighting feat is needed to be able to correctly fight with more than one weapon.
Second, does the Two-Weapon Fighting feat work with more than one off-hand? By the book, the answer would be MEH as it does specify that this feat is for Two Weapons. Yet, it don't say anything about more than two weapons… And so the rule does also apply with three or more weapon as each combination IS a Two-Weapon fighting style… So, by applying the rule, two case scenario:
- The feat apply on all attack as the feat apply to each off-hands weapons in combination with the primary weapon.
- The feat only apply to the first attack made with an off-hand weapon. Meaning that all others off-hands weapons take the full penalty on their attack roll.
The first case seem good, but then why would the Multiweapon Fighting feat exist?
And the second case seem quite strange… As the penalty is already quite heavy, why would we need to add a drawback on a weapon adding another off-hand attack?
Here again, the answer would be MEH… The conditions on the feat aren't even coherent with themselves: the special has a condition on the number on arms when the prerequisites have a condition on the number of hands… Because of that, yet again, two case scenario:
- The special condition should have used the word hands. In this case, having more off-hands could work.
- The prerequisites conditions should have used the word arms. In this case, having more off-hands won't work.
The most likely would be "hands" as that's the word generally used when considering fighting and other actions. And even the Tentacle and the Vestigial Arm discoveries make sure to use the word "hands" to describe the power.
Now the problem would be: Does an off-hand account for a hand in this case? And the answer is yet again MEH… In the context of the feat, which is to modify the penalty on off-hands attacks, it should be yes… But, the wording don't really make this clear.
4) Does the Blade Boot count as an extra off-hand weapon?
YES, it does.
Unlike for the Armor Spikes, it isn't specified otherwise.
Benefit: You can use a blade boot as an off-hand weapon.
And there is even a drawback to balanced the whole thing.
Drawback: When the blade is extended, you treat normal terrain as difficult and difficult terrain as impassable.
Just like the Barbazu Beard with said that you can make an extra off-hands attack, with a drawback too…
Attacking with a barbazu beard provokes an attack of opportunity. Because it is so close to the wearer’s face, using a barbazu beard against creatures harmful to touch (such as fire elementals and acidic oozes) has the same risks as using a natural weapon or unarmed strike against these creatures.
You can fight with all limbs using Blade Boot. But two scenario:
And in the end, we would need extra talents and/or feats to compensate the drawback.
By rewording all "two-weapon fighting" stuff as "Multi-weapon fighting", and making sure that we only use the word "off-hands" in descriptions, everything about that would be fixed… No more Multiweapon Fighting feat and the like needed. No more mess…