Weapon Eidolons
Some summoners prefer to have their eidolon not just close at hand, but in hand. These eidolons take the form of weapons rather than creatures, and do not possess skills, feats or ability scores.

A basic weapon eidolon is a melee weapon that deals damage of one type (slashing, bludgeoning or piercing) with a crit range of 20/x2, and has hardness 10 and 4hp, +4 hp for every summoner level you possess. It may take the form of a light, one-handed or two-handed weapon, dealing 1d4, 1d6 or 1d8 points of damage respectively. It possesses an enhancement bonus equal to half the summoner's class level (round up). Weapon eidolons choose their evolutions from a different list to standard eidolons.

Mastery (Ex): The summoner is always proficient with his weapon eidolon, and may use his summoner level in place of his BAB when attacking with it. This benefit does not apply if he attacks with weapons other than eidolon weapons as part of the same action, or if the weapon is wielded by another character.

Alertness: While wielding the weapon eidolon, the summoner gains the Alertness feat.

Fighter Training (Ex): At 6th level, the eidolon's master counts 1/2 his total summoner level as his fighter level for the purpose of qualifying for feats. If he has levels in fighter, these levels stack.

Dispelling Strike (Su): At 10th level, the summoner may spend a swift action to charge his weapon eidolon with energy for 1 round. He may discharge this energy after successfully striking a creature in order to create a targeted dispel magic effect with a caster level equal to his summoner level.

Dismissing Strike (Su): As Dispelling Strike, except that at 14th level the summoner can create a dismissal effect instead.

Planar Weapon (Su): At 18th level the summoner may extend his weapon eidolon into coterminous planes, or return it to his plane, as a free action. This allows it to strike creatures in these planes as if they were on the same plane as him.

1-Point Evolutions

• Additional Damage Type: The weapon's damage is considered to be another type (slashing, bludgeoning or piercing) in addition to its existing type. You may select this evolution twice.
  
• Double Weapon: This evolution may only be applied to a one-handed weapon. Your weapon eidolon takes the form of two one-handed weapons connected together. These weapons have the same enhancement bonus, but evolutions (except this one) must be applied to one end or the other. The penalties for dual-wielding both ends of your eidolon are the same as those for dual-wielding a one-handed weapon and a light weapon.
  
• Increased Critical Multiplier: The critical threat range of the weapon increases by 1. You may select this evolution twice. This evolution may not be combined with Increased Threat Range.
  
• Increased Damage: The weapon's damage dice increase by +1 size. You may select this evolution twice.
  
• Increased Threat Range: The critical threat range of the weapon increases by 1. You may select this evolution twice. This evolution may not be combined with Increased Critical Multiplier.
  
• Pull: Once per round, whenever you strike a creature with the eidolon weapon, you can attempt a free combat maneuver check. If successful, the target of the attack is pulled 5 feet closer to you. This ability only works on creatures of a size equal to or smaller than you. Creatures pulled in this way do not provoke attacks of opportunity. The eidolon weapon must have a reach of 10 feet or more to use this evolution. This evolution can be selected more than once, each time after the first giving you an additional use of the ability per round.
  
• Push: Once per round, whenever you strike a creature with the eidolon weapon, you can attempt a free combat maneuver check. If successful, the target of the attack is pushed 5 feet directly away from you. This ability only works on creatures of a size equal to or smaller than you. Creatures pushed in this way do not provoke attacks of opportunity. This evolution can be selected more than once, each time after the first giving you an additional use of the ability per round.
  
• Ranged: The eidolon can be used as a thrown weapon with a range increment of 30ft (light), 40ft (one-handed) or 50ft (two-handed), but takes a -4 penalty on melee attack rolls.
  If 1 additional evolution point is spent, it instead fires arrows as a composite bow matched to its wielder's Strength; its range increment is doubled but it can no longer be used to make melee attacks.
  
• Reach: The weapon threatens out to double your normal reach, but it does not threaten adjacent squares. If 1 additional evolution point is spent, it also threatens adjacent squares.
  

2-Point Evolutions

• Adamantine: The weapon is considered to be made of adamantine in addition to its normal type, allowing it to overcome certain types of DR and hardness.
  
• Cold Iron: The weapon is considered to be made of cold iron in addition to its normal type, allowing it to overcome certain types of DR.
  
• Grab: The eidolon becomes hooked or barbed, granting a grab attack. Once per round, when you hit a target with the weapon eidolon you can attempt a free combat maneuver check. If successful, you grapples the target. This ability only works on creatures of a size one category smaller than you or smaller. Eidolons with this evolution grant a +4 bonus on CMB checks made to grapple. This evolution can be selected more than once, each time after the first giving you an additional use of the ability per round.
  
• Poison: The eidolon secretes toxic venom, granting a poison attack. Once per round, when you hit a target with the weapon eidolon they become poisoned.
  
  Quote
  Eidolon poison—type 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 summoner's HD + the summoner's Constitution modifier.
  For 2 additional evolution points, this poison deals Constitution damage instead. The summoner must be at least 7th level before selecting this evolution. This evolution can be selected more than once, each time after the first giving you an additional use of the ability per round.
  
• Rend: The eidolon can be used to rip and tear the flesh of those you attack, granting the rend ability. Whenever you successfully hit the same target with two ends of a Double Weapon eidolon in 1 round, it latches onto the flesh and deals extra damage. This damage is equal to the damage dealt by one end of the eidolon plus 1-1/2 times your Strength modifier. The eidolon must possess the Double Weapon evolution to select this evolution. The summoner must be at least 6th level before selecting this evolution.
  
• Silver: The weapon is considered to be made of alchemical silver in addition to its normal type, allowing it to overcome certain types of DR.
  
• Trip: The eidolon becomes good at knocking foes to the ground, granting you a trip attack. Once per round, when you hit a target with the weapon eidolon you can attempt a free combat maneuver check. If successful, the target is knocked prone. If the check fails, you are not tripped in return. This ability only works on creatures of a size equal to or smaller than you. This evolution can be selected more than once, each time after the first giving you an additional use of the ability per round.
  

3-Point Evolutions

• Enchantment (Su): The weapon gains an enchantment equivalent to a +1 bonus. This may not be used to increase the weapon's enhancement bonus. You may select this evolution multiple times, and can combine multiple uses to gain weapon enhancements with higher values (eg. selecting this evolution twice would let you get a +2 equivalent ability).
  

4-Point Evolutions

• Breath Weapon (Su): You learn to expel a cone or line of magical energy from the eidolon weapon, similar to a breath weapon. Select either acid, cold, electricity, or fire. You may create a 30-foot cone (or 60-foot line) that deals 1d6 points of damage of the selected type per summoner level. Those caught in the breath weapon can attempt a Reflex save for half damage. The DC is equal to 10 + 1/2 your summoner level + your Constitution modifier. The eidolon may be used in this manner once per day. The eidolon can use this ability 1 additional time per day by spending an additional 1 evolution point (maximum 3/day). The summoner must be at least 9th level before selecting this evolution.
  
• Large: The weapon eidolon increases in size by one category, becoming Large. Its master (but not other creatures) can wield it as easily as before. The weapon's base damage increases by one size, and it gains +5ft reach. The bonus from Shield Ally increases by +2, and its master gains a +2 bonus to CMB and CMD. The eidolon must be Medium to take this evolution. The summoner must be at least 8th level before selecting this evolution.
  If 6 additional evolution points are spent, the eidolon instead becomes Huge. This provides double the bonuses provided by becoming Large. The summoner must be at least 13th level before selecting this option.
  

Weapon Eidolons and Broodmasters
A summoner with the Broodmaster archetype has multiple eidolons of reduced strength. Such a character may choose to make some or all of his eidolons into weapon eidolons. His lower effective summoner level reduces the strength of the eidolon's Mastery ability, but this never results in an effective BAB lower than his actual BAB.

A standard eidolon may gain the ability to wield a specific weapon eidolon as a 1-point evolution, gaining all benefits as if it were its master. The eidolon may do this only if the master of that weapon consents to it (since the other eidolon usually has the same master, this is rarely an issue).

Eidolon Master (archetype)
Advanced Eidolon: The summoner's eidolon possesses HD equal to his class level, with all the bonuses this grants (more BAB, saves, skill points, feats, etc.); it does not gain any additional evolution points or other benefits not tied to HD. In addition, at 4th, 8th, 12th, 16th and 20th levels the eidolon's Con score increases by 1. This replaces the summoner's spellcasting advancement at these levels - by lv20 he has the spells per day and spells known of a summoner 5 levels lower. The summoner's caster level is not reduced.

EDIT: Transferred from previous post


This is Paizo's fault for their confusing "class abilities only affect that class" rule.

Whoops...

I'll sort that out later. For now I was going for compatibility with Broodmaster.

Good catch.

Not quite. PF staffs have 10 charges and can have a charge recharged 1/day by expending a spell slot.

And another update - Eidolon Master.