Summoner Challenge: Grappling Eidolon

[Evershifter]

As a thought experiment, I've been thinking about making a summoner who generally does not have the eidolon in play, rather making liberal use of the SM ability. Got to thinking, what kind of eidolon would work well in an "Oh crap!" moment to help the party out?
A grappling eidolon would be a good one that you could keep from having to load too full of magic items that could pop out and control one tricky bad guy, right?

So here's the question:
Show a 20 level build for an eidolon optimized for grappling purposes (maybe swallowing too), making use of as few magic items as possible (assuming that a Strength belt will be required, but justify any others that make use of slots).

Go!

[Sleet Storm]

This build assumes a half elf summoner that takes Extra Evolutions at every opportunity(Levels 1/5/11/17)

:

Serpentine Base form
Level 1:Evolutions:Ability Increase(strenght),Gore Feat:Improv.Unarmed
Level 2:Evolutions:Natural armor+2
Level 3:Evolutions:Reach Feat:Power Attack
Level 4:Evolutions:Reset(throw out Reach)Grab,Constrict
Level 5:Evolutions:Nat.Armor+2,Sting
Level 6:Evolutions:Bite(1.5x Strenght)Feat:Improved Grapple
Level 7:Evolutions:Reach
Level 8:Evolutions:Reset(throw out Reach and Bite) Large
Level 9:Evolutions:Reset(Throw out Sting)Limbs(arms),Claws Feat:Greater Grapple
Level10:Evolutions:Nat.Armor+2
Level11:Evolutions:Ability Increase(strenght) Feat:Weapon Focus(Bite)
Level12:Evolutions:Sting,Bite
Level13:Evolutions:Tentacle
Level14:Evolutions:Reset(throw out 2xNat.Armor,Tentacle,Bite) Huge Feat:Furious Focus
Level15:Evolutions:Bite
Level16:Evolutions:2xNat.Armor+2
Level17:Evolutions:Tentacle,Sting Feat:Dazing Assault
Level18:Evolutions:Reach
Level19:Evolutions:Abilitiy Increase (strenght)
Level20:Evolutions:Mount,Tentacle

Half Elf alternate Favoured class bonus gives Extra evolution point at levels 4/8/12/16/20
Grapple CMB:42 +Grab+Constrict without buffing or magic items

[Sleet Storm]

Aargh,I messed up the feats but I can´t edit my post anymore.
Change Weapon Focus Bite to Final Embrace, Change Furious Focus to Rapid Grappler ,change Dazing Assault to Ability Focus(constrict) and add Final Embrace Master at level 19.

[deanruel]

This is actually absurdly simple in that there's really nothing different you would do for a grapple Eidolon that you wouldn't do for all of them.

Make them Huge, buff their strength till you hover around 50, take grab, take lots of claw attacks, take Rake.

So by level 20 you're looking at something like 6 Claw attacks at +40 to hit or so, each one granting you a free grapple attempt, and each of those grapple attempts grants you 2 free rake attacks.

CMB would be something above +40 and the kicker is with every attack you get a new try. So if you don't succeed by the first you make your second attack and so on. Really unless you miss all 6 attacks or all six grapple rolls you're locking people down. Eidolons are just murderkings.

[wraithstrike]

At level 20 many bad guys can teleport so keeping a hold of someone or something is much harder than it seem. A +40 means that if you roll a 10 you get a +50 grapple check.

Pit Fiends have a CMD of +53(I know they will still most likely get grappled with 6 rolls), and they can teleport at will.
Balors can teleport. That surprises me.
Tarn Linnorm has a CMD of 64 and Freedom on Movement so he can't be grappled.
Dragons will most likely have at least one teleport based spell known so they can get to the caster.
Any epic monsters, and you will probably meet a few are probably also able to avoid being held down.