So we got a medium sized four armed eidolon weilding an ogre's great club

[Rogar Stonebow]

He is using all of his four arms to wield it.

First, does it work?

Second, how does it work? (you know attack penalties and what not.)

Thirdly, if the Eidolon had six arms, could he wield a Storm Giant's Great sword?

Fourthly, how does that one work?

[kestral287]

By RAW, there's absolutely no mechanism for this. So everything here is GM fiat.

[wraithstrike]

No, it does not work.

[Amrel]

Rogar Stonebow wrote:

He is using all of his four arms to wield it.

First, does it work?

Second, how does it work? (you know attack penalties and what not.)

Thirdly, if the Eidolon had six arms, could he wield a Storm Giant's Great sword?

Fourthly, how does that one work?

It does not work. One handed weapons can be wielded with 2 hands, and 2 handed weapons can be wielded with 2 hands, but it is not ever possible to use more than 2 on any single weapon.

[Rogar Stonebow]

ok

[boring7]

Pretty sure it's not even sensible. In terms of damage output you have small attacks vs. 1 big one. And I can't think of a situation where having extra hands to wield an extra-big weapon passes the rule of cool.