The APG says "Armor Bonus: The number noted here is the eidolon's base total armor bonus. This bonus may be split between an armor bonus and a natural armor bonus, as decided by the summoner. This number is modified by the eidolon's base form and some options available through its evolution pool. An eidolon cannot wear armor of any kind, as the armor interferes with the summoner's connection to the eidolon."
Can anyone tell me why it would be better to have an armor bonus and not a natural armor bonus for an eidolon?
Armor Spikes: Can I use two-weapon fighting to make an "off-hand" attack with my armor spikes in the same round I use a two-handed weapon?
Just found it on the prd it says in equipment "Double Weapons: Dire flails, dwarven urgroshes, gnome hooked hammers, orc double axes, quarterstaves, and two-bladed swords are double weapons. A character can fight with both ends of a double weapon as if fighting with two weapons, but he incurs all the normal attack penalties associated with two-weapon combat, just as though the character were wielding a one-handed weapon and a light weapon.
The character can also choose to use a double weapon two-handed, attacking with only one end of it. A creature wielding a double weapon in one hand can't use it as a double weapon—only one end of the weapon can be used in any given round." don't know if that helps.