Reflecting their connected nature, a twinned summoner and his eidolon appear identical save for any obvious differences, such as evolutions or equipment.
The twinned summoner’s eidolon is restricted to the biped base form. An unchained summoner’s eidolon is instead restricted to the twinned eidolon subtype (see here). If the summoner’s natural size is smaller than Medium, the twinned summoner’s eidolon must be Small. This ability may require a different base form or subtype to match the twinned summoner’s natural form, at the GM’s discretion, if the twinned summoner is not a bipedal creature.
Teamwork Feats (Ex)
At 4th level and at 12th level, a twinned summoner gains a bonus teamwork feat. He must meet the prerequisites of the selected teamwork feat. The twinned summoner automatically grants all of his teamwork feats to his eidolon. The eidolon doesn’t need to meet the prerequisites of these teamwork feats.
This ability replaces shield ally and greater shield ally.
Twinned Transposition (Su)
At 6th level, as a standard action, a twinned summoner can swap locations with his eidolon as if each were using dimension door, using the twinned summoner’s caster level. If the eidolon is out of range, the ability is wasted. If either the twinned summoner or his eidolon occupies more squares than the other, each must occupy one or more squares that were occupied by the other if possible, or as close as possible if not. The twinned summoner can use this ability once per day at 6th level, plus one additional time per day for every 4 levels beyond 6th. At 8th level, he can use this ability as a swift action.
This ability replaces maker’s call and transposition.
Twin Summoner (Su)
At 16th level, a twinned summoner can touch his eidolon as a standard action, enhancing its similarity to the summoner. The eidolon loses any natural weapons or size increases gained from evolutions, and its Intelligence, Wisdom, and Charisma scores change to match the base scores of the summoner. The eidolon can cast any of the summoner’s spells known using the summoner’s caster level and spell slots. It doesn’t gain the benefit of any of the summoner’s items, feats, or other effects that affect spellcasting. The eidolon can keep this form for a number of minutes per day equal to the summoner’s class level. This duration does not need to be consecutive, but it must be spent in 1-minute increments. The summoner can end this effect as a free action.
This ability replaces the merge forms class feature.
Twinned Eidolon (Eidolon Subtype)
Just like a summoner, a twinned eidolon learns to use weapons and magic. While twinned eidolons are ethically more flexible than most eidolons, they are quite adamant about being treated as equals and not as servants. They demonstrate an eerie consistency with the summoner’s manner of thinking, providing similar answers to questions and reacting similarly to startling events. This subtype is restricted to twinned summoners.
Base Form: Biped (limbs [arms], limbs [legs]).
Base Evolutions: A twinned eidolon gains the weapon training evolution. The twinned eidolon also gains the skilled (Disguise) evolution. The racial bonus provided by this evolution is doubled when the eidolon is impersonating the twinned summoner.
At 4th level, a twinned eidolon can cast a summoner spell once per day as a spell-like ability. The spell must be one known by the eidolon’s summoner and must be at least 1 level lower than the highest-level spell the summoner can cast. The eidolon must have a Charisma score of at least 10 + the spell level. The caster level for this spell-like ability is equal to the eidolon’s Hit Dice minus 2. The save DC is 10 + half the eidolon’s HD + the eidolon’s Charisma modifier. At 8th level, a twinned eidolon gains the shared slot evolution (see below).
At 16th level, a twinned eidolon gains the skilled evolution and the ability increase evolution, applied to a skill and an ability score of the summoner’s choice.
At 20th level, a twinned eidolon gains fast healing 5.
Pathfinder Player Companion: Legacy of the First World © 2017, Paizo Inc.; Authors: Judy Bauer, John Compton, Violet Hargrave, Mikko Kallio, Jason Keeley, Joe Pasini, Mark Seifter, Kendra Leigh Speedling, Josh Vogt, and Linda Zayas-Palmer.