• FUSED EIDOLON: A synthesist summons the essence of a powerful outsider to meld with his own being. The synthesist wears the eidolon like translucent, living armor. The eidolon mimics all of the synthesist’s movements, and the synthesist perceives through the eidolon’s senses and speaks through its voice, as the two are now one creature.
While fused with his eidolon, the synthesist uses the eidolon’s physical ability scores (Strength, Dexterity, and Constitution), but retains his own mental ability scores (Intelligence, Wisdom, and Charisma). The synthesist gains the eidolon’s hit points as temporary hit points. When these hit points reach 0, the eidolon is killed and sent back to its home plane. The synthesist uses the eidolon’s base attack bonus, and gains the eidolon’s armor and natural armor bonuses and modifiers to ability scores. The synthesist also gains access to the eidolon’s special abilities and the eidolon’s evolutions. The synthesist is still limited to the eidolon’s maximum number of natural attacks. The eidolon has no skills or feats of its own. The eidolon must be at least the same size as the synthesist. The eidolon must have limbs for the synthesist to cast spells with somatic components. The eidolon’s temporary hit points can be restored with the rejuvenate eidolon spell.
While fused, the synthesist loses the benefits of his armor. He counts as both his original type and as an outsider for any effect related to type, whichever is worse for the synthesist. Spells such as banishment or dismissal work normally on the eidolon, but the synthesist is unaffected. Neither the synthesist nor his eidolon can be targeted separately, as they are fused into one creature. The synthesist and eidolon cannot take separate actions. While fused with his eidolon, the synthesist can use all of his own abilities and gear, except for his armor. In all other cases, this ability functions as the summoner’s normal eidolon ability (for example, the synthesist cannot use his summon monster ability while the eidolon is present).
This ability replaces the class’s eidolon ability, bond senses, and life bond.
The following class abilities function differently for synthesist summoners.
==Fused Link (Su)
Starting at 1st level, the synthesist forms a close bond with his eidolon. Whenever the temporary hit points from his eidolon would be reduced to 0, the summoner can, as a free action, sacrifice any number of his own hit points. Each hit point sacrificed this way prevents 1 point of damage done to the eidolon (thus preventing the loss of the summoner’s temporary hit points), preventing the eidolon from being killed and sent back to its home plane.
This ability replaces life link.
• SHADOW EIDOLON: A shadow caller's eidolon is at once a thing of shadow called from the deep of the Shadow Plane and his own shadow; the two are inseparable. When his eidolon manifests, his shadow lengthens and finally detaches from him as a creature unto itself. For as long as the shadow caller's eidolon is manifested, he and the eidolon do not have distinct shadows, regardless of the presence or absence of light. This lack of a shadow replaces the magical symbol that identifies the summoner and his eidolon.