I was thinking of going Synthesist with a biped eidolon to do TWF and go the Dimensional Dervish route. My main thought was that Synthesist get up to lvl 6 spells, and they can have awesome stats, so it could possibly work out well. The main issue is that I'm not sure they can do enough damage.
I know they can dish out crazy damage with natural attacks, but I'm not looking for natural attacks, nor am I looking for pounce with their quad form. I'm going biped + TWF for pure flavor, but those are must-haves. Also wanting Dimensional Dervish asap, and decent spellcasting (mainly for buffs and personal versatility, not for control or SoS or anything like that).
Extra arms are a 2 point evolution, simple weapon proficiency is 2 points, martial weapon proficiency is an extra 2 points, more than enough feats there, just a lack of dexterity. Ability score increase evolutions should take care of that though.
You can reach TWF with simple weapons by level 5, and ITWF with martial weapons by level 7.
Isn't multiweapon fighting the TWF for multiarmed creatures? The feat description says that it replaces it in such occasions.
Would you really need the weapon proficiency? Summoners already have simple weapon proficiencies, so you could just use daggers, couldn't you? That was always the trouble with synthesists: which proficiencies should you use? The summoner's, or the eidolons? Anyway, if you can just grab daggers from the get go, then it should be much easier to get into your style.
As a side note: you will want to leave one of your various arms free so that you can do casting. Maybe make it one of the default arms with the claws, so that it has something to do why you full attack.
|Ahuru Mazda XTREME|
This should work, and work quite well. You don't need the weapon proficiency evolutions: just use simple weapons, or use one of your feats for a martial/exotic weapon proficiency. Use your evolutions for the necessary dex increase, and you'll have a lot of evolutions left to do fun stuff with. I actually really like this idea.
The most efficient way of two-weapon fighting is probably one where you can use your main weapon two handed on standard attacks, and somehow conjure up a second weapon for off-hand attacks. This would also help with casting, as you will occasionally need a hand free for that as well. The best way to accomplish this is probably a glove of storing. Before you can afford that, you are somewhat stuck. You could pick up improved unarmed strike so you can punch for your off-hand attack, or you could use brass knuckles, which imposes a spell failure chance when you try to cast with that arm. You could also get the quick draw feat, and just carry a bunch of daggers to drop and quickdraw as required. It's a shame that all these options eat up a feat though, but you can probably spare it. Especially if you go human.
If you want to be wielding two weapons at all time, exotic weapon proficiency for kukris or wakizashis is probably a good idea, but it will make your spellcasting seriously annoying.
A synthesist certainly can do enough damage with just 2 weapons. Just keep your strength up with the ability increase evolution and eventually take the large evolution. Even if you only want to fight with 2 weapons you should get extra limbs to have hand free to cast spells. You might not do as much damage as a pouncing 8 clawed eidolon, but you will certainly legitimately contribute to the party.
I had somehow assumed you did not want to have more than two arms. If you do, a TWF synthesist is easy. Get some nice weapon proficiencies, wield a one handed weapon in your main hand, a light weapon in your off hand, put your third hand on your main weapon for 1.5x strength and power attack bonuses (this seems to be allowed RAW) and use your 4th hand to cast.
If you do want to have only two hands, it works as well, but is a bit harder. Here's my build:
half elf 8 synthesist / 1 lore warden / 11 synthesist
ability scores (20 pts): str 11, dex 15, con 14, int 10, wis 10, cha 15+2
1. two weapon fighting, exotic weapon proficiency falcata
5. power attack
7. dimensional agility
9. dimensional assault, improved two-weapon fighting
11. dimensional dervish
ability increase dex (lvl 2 & again at 8)
improved natural armor (as often as possible)
ability increase str (as often as possible)
At higher levels, you could also take more fighter levels to get some extra combat feats a bit quicker. The feats I'd get next are double slice, two weapon rend and greater two weapon fighting, in that order. Although arcane strike would be nice as well. But getting to synthesist 7 asap is important for access to the dimensional dervish feats, and synthesist 8 is great for large. The rest of your evolutions can be spend on whatever you like. I'd take the extra evolution points class bonus, and go to town with senses and resistances.
This character can do two weapon fighting from level 2 (at level 1 he qualifies for the feat in half-elf form, but cannot use it in synthesist form). With quickdraw he'll wield a falcata in one hand, and choose to either two-hand it on standard actions or quickdraw a dagger for full attacks, and then drop the dagger again. He can also throw daggers at full TWF rate. The only painful part is when you realize that once you can cast haste, you're actually better off not quickdrawing a dagger but full attacking two handed. Sadly, that problem cannot be solved until you get two weapon rend, as you don't have any good static sources of bonus damage.