At 1st level, all elemental eidolons gain immunity to paralysis and sleep. In addition, air elemental eidolons gain immunity (electricity) evolution. Earth elemental eidolons gain immunity (acid) evolution.
Fire elemental eidolons gain immunity (fire) evolution. Water elemental eidolons gain immunity (cold) evolution.
Immunity (Su) (Pathfinder Unchained pg. 37): The eidolon’s body becomes extremely resilient to one energy type. Select one energy type: fire. The eidolon gains immunity to that energy type. This evolution can be selected more than once. Its effects do not stack. Each time it applies to a different energy type. Requirements: Summoner level 7th.
Bite (Ex) (Pathfinder Unchained pg. 35): The eidolon’s maw is full of razor-sharp teeth, giving it a bite attack. This attack is a primary attack. The bite deals 1d6 points of damage (1d8 if Large, 2d6 if Huge). If the eidolon already has a bite attack, this evolution allows it to deal 1-1/2 times its Strength modifier on damage rolls made with its bite. Requirements: Agathion, daemon, demon, devil, div, elemental, protean, or psychopomp subtype.
Magic Attacks (Su) (Pathfinder Unchained pg. 35): The eidolon is infused with magic, allowing it to treat all of its natural attacks as if they were magic for the purpose of overcoming damage reduction. If the summoner is 10th level or higher, all of the eidolon’s natural attacks are treated as the alignment of the eidolon for the purpose of overcoming damage reduction.
(Ex) (Advanced Player's Guide pg. 61): One of an eidolon's attacks is capable of striking at foes at a distance. Pick one attack. The eidolon's reach with that attack increases by 5 feet.
Improved Natural Armor (Ex) (Pathfinder Unchained pg. 35): The eidolon’s hide grows thick fur, rigid scales, or bony plates, giving it a +2 bonus to its natural armor. This evolution can be taken once, plus one additional time for every 5 levels the summoner possesses. Each additional time it’s taken, the bonus increases by 2.
Darkvision (Ex): The eidolon has darkvision with a range of 60 feet.
Link (Ex): A summoner and his eidolon share a mental link allows for communication across any distance (as long as they are on the same plane). This communication is a free action, allowing the summoner to give orders to his eidolon at any time. In addition, magic items interfere with the summoner's connection to his eidolon. As a result, the summoner and his eidolon share magic item slots. For example, if the summoner is wearing a ring, his eidolon can wear no more than one ring. In case of a conflict, the items worn by the summoner remain active, and those used by the eidolon become dormant. The eidolon must possess the appropriate appendages to utilize a magic item.
Share Spells (Ex): The summoner may cast a spell with a target of “you” on his eidolon (as a spell with a range of touch) instead of on himself. A summoner can cast spells on his eidolon even if the spells normally do not affect creatures of the eidolon's type (outsider). Spells cast in this way must come from the summoner spell list. This ability does not allow the eidolon to share abilities that are not spells, even if they function like spells.
Evasion (Ex): If an eidolon is subjected to an attack that normally allows a Reflex save for half damage, it takes no damage if it makes a successful saving throw.
