Centaur
Source: Ultimate Magic
The eidolon has the upper torso of a humanoid and the lower body of a quadruped (such as a horse).A centaur eidolon’s upper humanoid torso is smaller than its quadrupedal body. As a result, it wields weapons as if it were one size category smaller than its actual size (Medium for most centaur eidolons). The centaur model can also be used to create a lamia (a centaur eidolon with the upper body of a woman and the lower body of a lion) by replacing the hooves evolution with claws and taking basic magic (touch of fatigue), minor magic (ventriloquism), major magic (daze monster), and ultimate magic (major image), resulting in a 23-point model.
13 points: Base Form quadruped; Primary Evolutions limbs (arms), hooves; Secondary Evolutions large, trample, weapon training, weapon training (martial).
Ok , this makes quite clear what the rules are if i want a centaur with a sword , but what about eidolons with many arms using natural attacks?
For the centaur itself is not so hard so divide this , assuming i got:
1 Great Sword -> Medium (arms)
2 Claws -> Medium (arms)
2 Hooves -> Large (legs)
Ok ... but what if i want the lamia?
1 Great Sword -> Medium (arms)
2 Claws -> Medium (arms)
2 Claws -> Large (legs)
And then what if i add rend? Which would be the claw damage i should use?
So my question is , what should be the weapon size for the natural attacks an centaur/lamia eidolon does?
You are already nerfing yourself for flavor by having certain parts of the Eidolon count as medium, eventhough you paid for the large evolution.
So it's really whatever you want. Up to large ;)
Notably, the d20 SRD Centaurs have large weapons, even though the Pathfinder ones do not. You could make an argument for large natural attacks for a centaur-like creature.
As for the damage the natural attacks do...
Medium claws do d4. Large d6. Quite a few bestiary creatures alter these numbers when appropriate. But by default these values.
For a lamia or centaur-like creature you could argue for large claws, but most true to the actual creature is medium.
Hum ic , so i should argue for the large natural attaks and keep the appearance a fluff factor ...
But is that really necessary?
I dont have a lot of experience with higher levels , where supposedly their damage become more "standard" , but for now mine gives a LOT of damage , i dont think using medium dices over large would make it fall behind.
Still , it would be "fair" (will talk with the GM anyway, but since im the one cheking most stuff about eidolons and rules) to go for:
Centaur/Lamia
1 Great Sword -> Medium (arms)
2 Claws -> Large (arms)
2 Claws -> Large (legs)
Matter of preference, really. The change it damage dice probably won't matter that much, since it'll still presumably have the muscle behind the attacks.
Neither the Centaur nor Lamia have claws on their humanoid bodies, as humans do not have claws. Nothing stops an Eidolon who happens to resemble them from doing so, though. I just imagine a more bestial version. Won't be able to use them with a sword occupying the hands, though.
Matter of preference, really. The change it damage dice probably won't matter that much, since it'll still presumably have the muscle behind the attacks.
Neither the Centaur nor Lamia have claws on their humanoid bodies, as humans do not have claws. Nothing stops an Eidolon who happens to resemble them from doing so, though. I just imagine a more bestial version. Won't be able to use them with a sword occupying the hands, though.
Yeah damage wize unless the eidolon becomes huge , i dont see a big dif either.
1d4 (notmal medium)
1d6 (Improved Natural Attack or Improved Damage , i heard you cant stack them together)
1d8 (Large)
2d6 (Huge)
So the damage only becomes 2d6 in this case if i went all the way up to huge anyway.
And what you said is true hehe , but i guess using 2 evo points to have another set of hands is not that costy in this case.
I would argue that being allowed to let your large eidolon wield medium sized weapons can be an advantage. Randomly generated loot usually contains small or medium weapons and when you fight an npc who might wield a useful magic weapon to loot afterwards, that pc is most likely to be medium sized as well. So you will get around much cheaper with weapons, while sacrificing, one maybe two points of damage per attack.
It would be nice if there was a small limbs evolution of some sort, that causes weapons and natural attacks to be a size category smaller on those limbs, and instead you get something else out of it (not sure what, i don't think that would be worth getting the evolution point back, unless all other benefits of those limbs other than being able to wield weapons/have natural attacks are also removed)
With the prebuilt cenatur on which this is only fluff based only the wielded weapons are smaller size category, natural weapons should still be that of your actual size.