Ive thought of what abilities would be replaced by what.
Chosen Soul-bound
(functions as a synthesist summoner except for where noted)
summon-> You can no longer summon a monster whose alignment is more than one step away from your Soul-Bound Eidolan.
Summoner spells-> After first level, your spells per day, spells known, and caster level are treated as if you are one level lower then you are.
Eidolan->Soul-Bound Eidolan. This functions as a fused Eidolan except for where noted. You choose an alignement for your soul-bound Eidolan at first level. This can't be more than one step away from yours. You must choose the biped base form. Your soul-bound eidolan has different stat progressions and abillities then a fused eidolan. These are detailed below. Your Eidolan is not sent to another plane when banished or dismissed. It resides in your soul when not in use. As such, you can speak telepathically.
Makers call->weapon experience: You gain the benefit of the exotic proficiency feat
Makers Jump->Skilled Eidolan: You can choose to use your Eidolans mental scores in place of yours, when making a skill check.
Aspect->improved weapon experience: You gain the benefit of the improved critical feat. If you already have it, you gain the bleeding critical feat instead.
Greater aspect-> You gain the benefit of the weapon focus and weapon specialization feats. If you already have one or both of these, you gain the greater versions instead.
twin eidolan-> You fuse permanently with your Eidolan. You keep your fusion when you are unconsious, and your health points are combined. You keep the attribute stat of your Soul-bound chosen or soul-bound eidolan, whichever is higher. If you die, because soul is combined with the eidolan, you find another summoner whose alignment is within one step of yours and become his eidolan. You now play as this character. This effect functions as the reincarnate spell, except you have a random new alignment within one step of your old one, and you have a new personality and set of memories.
Soul-bound Eidolan
Darkvision and devotion->arcane pool (this functions as the magus abillity)
link->Spell combat (as the magus abillity)
Share spells->Your Eidolan has the abillity to cast spells as a magus that is one level less than the Eidolans HD. while fused with your Soul-bound chosen, you can cast spells as the eidolan, using the eidolans intelligence, or as the soul-bound chosen, using the chosens charisma. Either works with spell combat and spell strike. Any spell cast by the soul-bound chosen, or soul-bound eidolan works on either.
Evasion->spell strike
Multiattack->improved spell combat
improved evasion->greater spell combat
After level one, your eidolan functions as an eidolan one HD less than it is.
Examples of story ideas for Soul-bound Chosen
Hervor, The Angel of Swans, was a force to be reckoned with on the battlefield. Wielding a combination of magic, steel, and her own divine might, she destroyed armies of demons singlehanded. When she finally was captured by the demon king, and forced into the realm of pure arcana, the elemental forces tore her body apart. Nations mourned. Despite this, numerous times has it been documented, when a young priest is studying the outer planes and the way they connect with the world, and when disaster strikes, he turns from meek theologian to divine champion, wearing the form of Hervor herself, as armor.
Jakob was investigating (robbing) the home of a wealthy mage who had died recently. In his tower he found many books of strange secrets, and reading them, he found he could understand them easily. In one of the deeper, darker places in the home of the dead wizard, he found something amazing. There was a circle, written on the floor in chalk, and strange symbols all around. Inside the circle was the bones of a demon. A strange vapor twisted above it, moving constantly from one side of the circle to the other. Jakob, curious, stepped forward and scuffed the chalk with his boot. Suddenly the vapor took the shape of a terrible demon, and it shreaked, for joy of being free, as it possessed it's savior. Ever since then, when Jakob needed to (or wanted to) he could take on the form of the demon and lay waste to his enemies with magic and claw.
A certain powerful lightning Azata had been kicked out of his home when he had proven to his father that he was not worthy of his power. His identity was put into his own hammer and thrown to midgard. When Dr. Donald Blake found the hammer, he felt instantly a strange presence. When he picked the hammer up, the precence forced itself inside his body, and turned it to a form that suited its purpose. He became THOR! GOD OF THUNDER!
