The Eidolon with a Thousand Blades

[Entropi]

It is specifically stated that the limit on the Eidolons attacks per round is specifically for natural attacks, and not for weapons. Can, say, an Eidolon with ten arms (possible around lvl 4-5) and ten weapons and the Multiweapon Fighting feat from the Bestiary then get 10 attacks per round?

[Jen the GM]

Yes, if you look at some of the summoning guides (Saph's is a good one), it will detail the ideas for such a build.

[Mnemaxa]

Sure.

At level 11, if you spend most of your evolutions on limbs and claws, it's entirely possible to build the multiattack eidolon.

That also means you do not get to spend those evolutions on size increases, damage increases, or defenses because you'll need almost all of them for limbs and pounce. It also means that with each attack you are at -2 for every natural attack and -2 for one weapon attack in addition -6 for every off hand weapon attack using the eidolon's 3/4 BAB attack bonus. Any non-weapon magic item you get for the eidolon is a magic item that most likely cannot be used by the summoner, so be careful with your allocations.

So basically what you are creating is the total-miss-monster.