Archives of Nethys

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Eidolon (Unchained) Details | Base Forms | Evolutions | Subtypes

Evolutions

Description Source: Pathfinder Unchained
Each eidolon gains a number of evolution points that can be spent to give the eidolon new abilities, powers, and other upgrades. These abilities, called evolutions, can be changed whenever the summoner gains a new level, but they are otherwise set. Some evolutions require that the eidolon have a specific base form or the summoner be of a specific level before they can be chosen. A number of evolutions grant the eidolon additional natural attacks. Natural attacks listed as primary are made using the eidolon’s full base attack bonus and add the eidolon’s Strength modifier on damage rolls. Natural attacks listed as secondary are made using the eidolon’s base attack bonus – 5 and add 1/2 the eidolon’s Strength modifier on damage rolls (if positive). If the eidolon has only a single natural attack, the attack is made using its full base attack bonus, and it adds 1-1/2 times its Strength modifier on damage rolls made with that attack, regardless of the attack’s type.

Evolutions are grouped by their cost in evolution points. Evolution points cannot be saved. All of the points must be spent whenever the summoner gains a level. Unless otherwise noted, each evolution can be selected only once.

1-Point Evolutions

The following evolutions cost 1 point from the eidolon's evolution pool.

Bite (Ex) (Pathfinder Unchained pg. 35 (Amazon)): 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.
Claws (Ex) (Pathfinder Unchained pg. 35 (Amazon)): The eidolon has a pair of vicious claws at the ends of its limbs, giving it two claw attacks. These attacks are primary attacks. The claws deal 1d4 points of damage (1d6 if Large, 1d8 if Huge). The eidolon must have the limbs evolution to take this evolution. This evolution can be selected more than once, up to the number of limbs evolutions the eidolon possesses. This evolution can be applied to any number of limbs (arms) evolutions, but no more than one limbs (legs) evolution. Requirements: Agathion, daemon, demon, devil, div, elemental, protean, or psychopomp subtype.
Climb (Ex) (Pathfinder Unchained pg. 35 (Amazon)): The eidolon becomes a skilled climber, gaining a climb speed equal to its base speed. This evolution can be selected more than once. Each additional time it is selected, increase the eidolon’s climb speed by 20 feet.
Gills (Ex) (Pathfinder Unchained pg. 35 (Amazon)): The eidolon has gills and can breathe underwater indefinitely.
Improved Damage (Ex) (Pathfinder Unchained pg. 35 (Amazon)): One of the eidolon’s natural attacks is particularly deadly. Select one natural attack form and increase the damage die by one step. This evolution can be selected more than once. Its effects do not stack. Each time the eidolon selects this evolution, it applies to a different natural attack.
Improved Natural Armor (Ex) (Pathfinder Unchained pg. 35 (Amazon)): 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.
Magic Attacks (Su) (Pathfinder Unchained pg. 35 (Amazon)): 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.
Mount (Ex) (Pathfinder Unchained pg. 35 (Amazon)): The eidolon is properly skilled and formed to serve as a combat-trained mount. The eidolon must be at least one size category larger than its rider. Requirements: Daemon, demon, devil, elemental, or protean subtype; quadruped or serpentine base form.
Pincers (Ex) (Pathfinder Unchained pg. 35 (Amazon)): An eidolon grows large pincers at the ends of one pair of its limbs, giving it two pincer attacks. These attacks are secondary attacks. The pincers deal 1d6 points of damage (1d8 if Large, 2d6 if Huge). Eidolons with the grab evolution linked to their pincers gain a +2 bonus on combat maneuver checks to grapple. The eidolon must have the limbs (arms) evolution to take this evolution. Alternatively, the eidolon can replace the claws from its base form with pincers (this still costs 1 evolution point). This evolution can be selected more than once, up to the number of limbs (arms) evolutions the eidolon possesses. Requirements: Agathion, daemon, demon, devil, div, elemental, protean, or psychopomp subtype.
Pull (Ex) (Pathfinder Unchained pg. 35 (Amazon)): The eidolon gains the ability to pull creatures closer with a successful attack. Select one type of natural attack. Whenever the eidolon makes a successful attack of the selected type, it can attempt a free combat maneuver check. If the eidolon succeeds at this check, it pulls the target of the attack 5 feet closer to it. This ability works only on creatures of a size category equal to or smaller than the eidolon. Creatures pulled in this way do not provoke attacks of opportunity. This evolution can be selected more than once. Its effects do not stack. Each time an eidolon selects this evolution, it applies to a different natural attack. Requirements: Reach of 10 feet or more.
Push (Ex) (Pathfinder Unchained pg. 35 (Amazon)): The eidolon gains the ability to push creatures away with a successful attack. Select one type of natural attack. Whenever the eidolon makes a successful attack of the selected type, it can attempt a free combat maneuver check. If the eidolon succeeds at this check, it pushes the target of the attack 5 feet directly away from it. This ability works only on creatures of a size category equal to or smaller than the eidolon. Creatures pushed in this way do not provoke attacks of opportunity. This evolution can be selected more than once. Its effects do not stack. Each time an eidolon selects this evolution, it applies to a different natural attack.
Reach (Ex) (Pathfinder Unchained pg. 36 (Amazon)): One of the eidolon’s attacks is capable of striking foes at a distance. Select one attack. The eidolon’s reach with that attack increases by 5 feet.
Resistance (Ex) (Pathfinder Unchained pg. 36 (Amazon)): The eidolon’s form takes on a resiliency to one particular energy type, which is usually ref lected in its physical body (ashen hide for fire, icy breath for cold, and so on). Select one energy type (acid, cold, electricity, fire, or sonic). The eidolon gains resistance 5 against that energy type. This resistance increases by 5 for every 5 levels the summoner possesses, to a maximum of 15 at 10th level. This evolution can be selected more than once. Its effects do not stack. Each time the eidolon selects this evolution, it applies to a different energy type.
Scent (Ex) (Pathfinder Unchained pg. 36 (Amazon)): The eidolon’s sense of smell becomes quite acute. The eidolon gains the scent special quality, allowing it to detect opponents within 30 feet by sense of smell. If the opponent is upwind, the range increases to 60 feet; if the opponent is downwind, the range drops to 15 feet. Strong scents can be detected at twice the normal range. Scent does not allow the eidolon to precisely locate the creature, only to detect its presence. It can detect the direction as a move action. The eidolon can pinpoint the creature’s location if it is within 5 feet. The eidolon can use scent to track creatures.
Shared Evolution (Su) (Legacy of the First World pg. 19): Select a 1-point or 2-point evolution the eidolon has. As a standard action, the eidolon can touch the summoner and transfer the selected evolution to him. This functions as the summoner’s aspect ability, and the same limitations apply. The summoner can touch the eidolon as a standard action to return the evolution. The evolution returns to the eidolon automatically if the eidolon is dismissed by the summoner or sent back to its home plane. Requirements: Twinned eidolon.
Skilled (Ex) (Pathfinder Unchained pg. 36 (Amazon)): The eidolon becomes especially adept at a specific skill, gaining a +8 racial bonus on that skill. This evolution can be selected more than once. Its effects do not stack. Each time the eidolon selects this evolution, it applies to a different skill.
Slam (Ex) (Pathfinder Unchained pg. 36 (Amazon)): The eidolon can deliver a devastating slam attack. This attack is a primary attack. The slam deals 1d8 points of damage (2d6 if Large, 2d8 if Huge). The eidolon must have the limbs (arms) evolution to take this evolution. Alternatively, the eidolon can replace the claws from its base form with this slam attack (this still costs 1 evolution point). This evolution can be selected more than once, up to the number of the eidolon’s limbs (arms) evolutions.
Sting (Ex) (Pathfinder Unchained pg. 36 (Amazon)): The eidolon possesses a long, barbed stinger at the end of its tail, granting it a sting attack. This attack is a primary attack. The sting deals 1d4 points of damage (1d6 if Large, 1d8 if Huge). This evolution can be selected more than once, up to the number of tail evolutions the eidolon possesses. Requirements: Agathion, daemon, demon, devil, div, elemental, protean, or psychopomp subtype; tail evolution.
Swim (Ex) (Pathfinder Unchained pg. 36 (Amazon)): The eidolon gains webbed hands, webbed feet, or powerful flippers, giving it a swim speed equal to its base speed. This evolution does not give the eidolon the ability to breathe underwater. This evolution can be selected more than once. Each additional time it is selected, increase the eidolon’s swim speed by 20 feet.
Tail (Ex) (Pathfinder Unchained pg. 36 (Amazon)): The eidolon grows a long, powerful tail. This grants it a +2 racial bonus on Acrobatics checks to balance on a surface. This evolution can be selected more than once. Requirements: Agathion, daemon, demon, devil, div, elemental, protean, or psychopomp subtype.
Tail Slap (Ex) (Pathfinder Unchained pg. 36 (Amazon)): The eidolon can use its tail to bash nearby foes, granting it a tail slap attack. This attack is a secondary attack. The tail slap deals 1d6 points of damage (1d8 if Large, 2d6 if Huge). This evolution can be selected more than once, up to the number of tail evolutions the eidolon possesses. Requirements: Agathion, daemon, demon, devil, div, elemental, protean, or psychopomp subtype; tail evolution.
Tentacle (Ex) (Pathfinder Unchained pg. 36 (Amazon)): The eidolon possesses a long, sinuous tentacle, granting it a tentacle attack. This attack is a secondary attack. The tentacle attack deals 1d4 points of damage (1d6 if Large, 1d8 if Huge). This evolution can be selected more than once. Requirements: Daemon, demon, or protean subtype.
Wing Buffet (Ex) (Pathfinder Unchained pg. 36 (Amazon)): The eidolon learns to use its wings to batter foes, granting it two wing buffet attacks. These attacks are secondary attacks. The wing buffets deal 1d4 points of damage (1d6 if Large, 1d8 if Huge). Requirements: Flight (wings) evolution.

2-Point Evolutions

The following evolutions cost 2 points from the eidolon's evolution pool.

Ability Increase (Ex) (Pathfinder Unchained pg. 36 (Amazon)): The eidolon grows larger muscles, gains faster reflexes, achieves greater intelligence, or acquires another increase to one of its abilities. Increase one of the eidolon’s ability scores by 2. This evolution can be selected more than once. It can be applied only once to an individual ability score, plus one additional time for every 6 levels the summoner possesses.
Constrict (Ex) (Pathfinder Unchained pg. 36 (Amazon)): The eidolon gains powerful muscles that allow it to crush those it grapples. Whenever the eidolon successfully grapples a foe using the grab evolution, it deals additional damage equal to the amount of damage dealt by the attack the grab evolution is tied to. Requirements: Serpentine base form, grab evolution.
Energy Attacks (Su) (Pathfinder Unchained pg. 36 (Amazon)): The eidolon’s attacks become charged with energy. Select one energy type: acid, cold, electricity, or fire. All of the eidolon’s natural attacks deal 1d6 points of energy damage of the chosen type on a successful hit. Requirements: Summoner level 5th.
Extra Feat (Ex) (Legacy of the First World pg. 19): The eidolon gains an extra feat. It must meet the prerequisites of the feat. Requirements: Twinned eidolon.
Flight (Ex or Su) (Pathfinder Unchained pg. 37 (Amazon)): The eidolon grows large wings, like those of a bat, bird, insect, or dragon, gaining the ability to fly. The eidolon gains a fly speed equal to its base speed. The eidolon’s maneuverability depends on its size. Medium or smaller eidolons have good maneuverability. Large eidolons have average maneuverability, while Huge eidolons have poor maneuverability. For 2 additional evolution points, the eidolon flies by means of magic. It loses its wings, but its maneuverability increases to perfect. If the eidolon flies by magic, this is a supernatural ability. The eidolon can increase its fly speed by spending additional evolution points, gaining a 20-foot increase to its fly speed for each additional point spent. Requirements: Summoner level 5th.
Gore (Ex) (Pathfinder Unchained pg. 37 (Amazon)): The eidolon grows a number of horns on its head, giving it a gore attack. This attack is a primary attack. The gore deals 1d6 points of damage (1d8 if Large, 2d6 if Huge). Requirements: Agathion, daemon, demon, devil, div, elemental, protean, or psychopomp subtype.
Grab (Ex) (Pathfinder Unchained pg. 37 (Amazon)): The eidolon becomes adept at grappling foes, gaining the grab ability. Select one of the following attacks: bite, claw, pincers, slam, tail slap, or tentacle. Whenever the eidolon makes a successful attack of the selected type, it can attempt a free combat maneuver check. If successful, the eidolon grapples the target. This ability works only on creatures at least one size category smaller than the eidolon. Eidolons with this evolution gain a +4 bonus on combat maneuver checks to grapple.
Immunity (Su) (Pathfinder Unchained pg. 37 (Amazon)): The eidolon’s body becomes extremely resilient to one energy type. Select one energy type: acid, cold, electricity, fire, or sonic. 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.
Limbs (Ex) (Pathfinder Unchained pg. 37 (Amazon)): The eidolon grows an additional pair of limbs. These limbs can take one of two forms. They can be made into legs, complete with feet. Each pair of legs increases the eidolon’s base speed by 10 feet. Alternatively, they can be made into arms, complete with hands. The eidolon does not gain any additional natural attacks for an additional pair of arms, but it can take other evolutions that add additional attacks (such as claws or slam). Arms that have hands can be used to wield weapons, if the eidolon is proficient. This evolution can be selected more than once.
Poison (Ex) (Pathfinder Unchained pg. 37 (Amazon)): The eidolon secretes toxic venom, gaining a poison attack. Select one bite or sting attack. Whenever the selected attack hits, the target is poisoned.

Eidolon Poison: Injury; save Fort negates; frequency 1/round for 4 rounds; effect 1d4 Str damage; cure 1 save.

The save DC is equal to 10 + 1/2 the eidolon’s Hit Dice + the eidolon’s Constitution modifier. For 2 additional evolution points, this poison deals Constitution damage instead. This poison can be used no more than once per round. Requirements: Summoner level 7th; daemon, demon, devil, elemental, or protean subtype; bite or sting evolution.
Rake (Ex) (Pathfinder Unchained pg. 37 (Amazon)): The eidolon grows dangerous claws on its feet, allowing it to make two rake attacks against foes it is grappling. These attacks are primary attacks. The eidolon can make these additional attacks each time it succeeds at a grapple check against the target. These rake attacks deal 1d4 points of damage (1d6 if Large, 1d8 if Huge). This evolution counts as one natural attack toward the eidolon’s maximum. Requirements: Summoner level 4th, quadruped base form.
Rend (Ex) (Pathfinder Unchained pg. 37 (Amazon)): The eidolon learns to rip and tear the flesh of those it attacks with its claws, gaining the rend ability. Whenever the eidolon makes two successful claw attacks against the same target in 1 round, its claws latch on to the flesh and deal extra damage. This damage is equal to the damage dealt by one claw attack plus 1-1/2 times the eidolon’s Strength modifier. Requirements: Summoner level 6th, claws evolution.
Shared Slot (Su) (Legacy of the First World pg. 19): Select a magic item slot. A magic item worn by the eidolon in that slot remains active even if the summoner is also wearing a magic item in that slot. This evolution can be selected more than once. Each time an eidolon selects this evolution, it applies to a new slot. Requirements: Twinned eidolon.
Trample (Ex) (Pathfinder Unchained pg. 37 (Amazon)): The eidolon gains the ability to crush its foes underfoot, gaining the trample ability. As a full-round action, the eidolon can overrun any creature that is at least one size category smaller than itself. This works like the overrun combat maneuver, but the eidolon does not need to attempt a check; it merely has to move over opponents in its path. The creatures take 1d6 points of damage (1d8 if Large, 2d6 if Huge), plus 1-1/2 times the eidolon’s Strength modif ier. Targets of the trample can make attacks of opportunity at a –4 penalty. If a target forgoes this attack of opportunity, it can attempt a Reflex save for half damage. The DC of this save is 10 + 1/2 the eidolon’s Hit Dice + the eidolon’s Strength modifier. A trampling eidolon can deal trampling damage to a specific creature only once per round. Requirements: Biped or quadruped base form.
Tremorsense (Ex) (Pathfinder Unchained pg. 37 (Amazon)): The eidolon becomes attuned to vibrations in the ground, gaining tremorsense with a range of 30 feet. This works like the blindsense evolution, but only if both the eidolon and the creature to be pinpointed are in contact with the ground. Requirements: Summoner level 7th.
Trip (Ex) (Pathfinder Unchained pg. 37 (Amazon)): The eidolon becomes adept at knocking foes to the ground with its bite, granting it a trip attack. Whenever the eidolon makes a successful bite attack, it can attempt a free combat maneuver check. If the eidolon succeeds at this check, the target is knocked prone. If the eidolon fails, it is not tripped in return. This ability works only on creatures of a size category equal to or smaller than the eidolon. Requirements: Daemon, demon, devil, elemental, or protean subtype; bite evolution.
Weapon Training (Ex) (Pathfinder Unchained pg. 37 (Amazon)): The eidolon learns to use a weapon, gaining Simple Weapon Proficiency as a bonus feat. If 2 additional evolution points are spent, it gains proficiency with all martial weapons as well.

3-Point Evolutions

The following evolutions cost 3 points from the eidolon's evolution pool.

Blindsense (Ex) (Pathfinder Unchained pg. 38 (Amazon)): The eidolon’s senses become incredibly acute, giving it blindsense with a range of 30 feet. This ability allows the eidolon to pinpoint the location of creatures that it can’t see without having to attempt a Perception check, but such creatures still have total concealment from the eidolon. Visibility still affects the eidolon’s movement, and it is still denied its Dexterity bonus to Armor Class against attacks from creatures it cannot see. Requirements: Summoner level 9th.
Burrow (Ex) (Pathfinder Unchained pg. 38 (Amazon)): The eidolon grows thick and gnarled claws, allowing it to move through the earth. The eidolon gains a burrow speed equal to 1/2 its base speed. It can use this speed to move through clay, dirt, earth, and sand. It does not leave a hole behind, nor is its passage marked on the surface. Requirements: Summoner level 9th.
Damage Reduction (Su) (Pathfinder Unchained pg. 38 (Amazon)): The eidolon’s body becomes more resistant to harm. Increase the damage reduction granted by the eidolon’s subtype by 5. Requirements: Summoner level 15th, damage reduction granted by the eidolon’s subtype.
Frightful Presence (Ex) (Pathfinder Unchained pg. 38 (Amazon)): The eidolon becomes unsettling to its foes, gaining the frightful presence ability. The eidolon can activate this ability as part of an offensive action, such as a charge or attack. Opponents within 30 feet of the eidolon must succeed at a Will save or become shaken for 3d6 rounds. The DC of this save is equal to 10 + 1/2 the eidolon’s Hit Dice + the eidolon’s Charisma modifier. If the eidolon has at least 4 more Hit Dice than an opponent that fails this save, that opponent becomes frightened instead. Foes with more Hit Dice than the eidolon are immune to this effect. Requirements: Summoner level 11th.
Pounce (Ex) (Pathfinder Unchained pg. 38 (Amazon)): The eidolon gains quick reflexes, allowing it to make a full attack after a charge. Requirements: Summoner level 7th, quadruped base form.
Swallow Whole (Ex) (Pathfinder Unchained pg. 38 (Amazon)): The eidolon gains the swallow whole ability, giving it the ability to consume its foes. If the eidolon begins its turn with a creature grappled using its bite attack (see the grab evolution), it can attempt a combat maneuver check to swallow the creature. The creature must be at least one size category smaller than the eidolon. Swallowed creatures take an amount of bludgeoning damage equal to the eidolon’s bite damage each round + 1d6 points of damage. A swallowed creature keeps the grappled condition, but can attempt to cut its way free with a light piercing or slashing weapon. The amount of damage needed to cut free is equal to 1/10 the eidolon’s total hit points. The eidolon’s AC against these attacks is equal to 10 + 1/2 its natural armor bonus. If a swallowed creature cuts its way out, the eidolon loses this ability until it heals this damage. Alternatively, the swallowed creature can attempt to escape the grapple as normal. Success indicates that it has returned to the eidolon’s mouth, where it can attempt to escape or can be swallowed again. Requirements: Summoner level 9th; agathion, daemon, demon, devil, div, elemental, protean, or psychopomp subtype; grab (bite) evolution.
Web (Ex) (Pathfinder Unchained pg. 38 (Amazon)): The eidolon gains a pair of spinnerets, giving it the ability to spin webs. The eidolon can use these webs to support itself plus one creature of up to the same size. It can throw webbing as a ranged touch attack up to eight times per day, entangling a creature up to one size larger than the eidolon. The webbing has a range of 50 feet and a 10-foot range increment. Creatures entangled by the web can escape with a successful Escape Artist check, or with a Strength check at a –4 penalty. The DC of these checks is equal to 10 + 1/2 the eidolon’s Hit Dice + the eidolon’s Constitution modifier. The webs have a hardness of 0 and a number of hits points equal to the eidolon’s total Hit Dice. The eidolon can climb its own webs at its climb speed and can pinpoint the location of any creature touching its webs. Requirements: Summoner level 7th; daemon, demon, or protean subtype; climb evolution.

4-Point Evolutions

The following evolutions cost 4 points from the eidolon's evolution pool.

Blindsight (Ex) (Pathfinder Unchained pg. 38 (Amazon)): The eidolon’s senses sharpen even further, granting it blindsight with a range of 30 feet. The eidolon can maneuver and attack as normal, ignoring darkness, invisibility, and most forms of concealment as long as it has line of effect to the target. Requirements: Summoner level 11th, blindsense evolution.
Breath Weapon (Su) (Pathfinder Unchained pg. 38 (Amazon)): The eidolon learns to exhale a cone or line of magical energy, gaining a breath weapon. Select acid, cold, electricity, or fire. The eidolon can breathe a 30-foot cone (or 60-foot line) that deals 1d6 points of damage of the selected type per Hit Dice it possesses. Those caught in the breath weapon can attempt a Ref lex save for half damage. The DC is equal to 10 + 1/2 the eidolon’s Hit Dice + the eidolon’s Constitution modifier. The eidolon can use this ability once per day. The eidolon can gain additional uses of this ability per day by spending 1 evolution point per additional use (to a maximum of three total uses per day). Requirements: Summoner level 9th.
Fast Healing (Su) (Pathfinder Unchained pg. 38 (Amazon)): The eidolon’s body gains the ability to heal wounds very quickly, giving it fast healing 1. The eidolon heals 1 point of damage per round, just like via natural healing. Fast healing does not restore hit points lost due to starvation, thirst, or suffocation, nor does it allow the eidolon to regrow lost body parts (or to reattach severed parts). Fast healing functions as long as the eidolon is alive. This fast healing does not function when the eidolon is not on the same plane as its summoner. This healing can be increased by 1 point per round for every 2 additional evolution points spent (to a maximum of 5 points per round). Requirements: Summoner level 11th.
Large (Ex) (Pathfinder Unchained pg. 39 (Amazon)): The eidolon grows in size, becoming Large. The eidolon gains a +4 bonus to Strength, a +2 bonus to Constitution, and a +2 bonus to its natural armor. It takes a –2 penalty to Dexterity. This size change also gives the creature a –1 size penalty to AC and on attack rolls, a +1 bonus on combat maneuver checks and to CMD, a –2 penalty on Fly checks, and a –4 penalty on Stealth checks. If the eidolon has the biped base form, it also gains a reach of 10 feet. Any reach evolutions the eidolon possesses are added to this total.

If 6 additional evolution points are spent, the eidolon instead becomes Huge. The eidolon gains a +8 bonus to Strength, a +4 bonus to Constitution, and a +5 bonus to its natural armor. It takes a –4 penalty to Dexterity. This size change also gives the creature a –2 size penalty to AC and on attack rolls, a +2 bonus on combat maneuver checks and to CMD, a 10-foot reach, a –4 penalty on Fly checks, and a –8 penalty on Stealth checks. If the eidolon has the biped base form, its reach increases to 15 feet instead of 10 feet. Any reach evolutions the eidolon possesses are added to this total. These bonuses and penalties replace, and do not stack with, those gained from becoming Large.

The ability increase evolution costs twice as much (4 evolution points) when adding to the Strength or Constitution scores of a Large or Huge eidolon. Requirements: Summoner level 8th (13th for Huge), Medium size.
Spell Resistance (Ex) (Pathfinder Unchained pg. 39 (Amazon)): The eidolon is protected against magic, gaining spell resistance. The eidolon’s spell resistance is equal to 11 + the summoner’s level. This spell resistance does not apply to spells cast by the summoner. Requirements: Summoner level 9th.