Creatures with Extradimensional Storage

[Morof Stonehands]

Are there any creatures that have any sort of innate extra dimensional storage?

This is for 3.5, any printed source is fine even dragon/dungeon.

[Doctor Despair]

Psions have an ACF to get extra dimensional space in their body that scales with leve

Scaled Ones can take a feat to get non-extra dimensional space in their body

[Athan Artilliam]

Give me a screwdriver, a portable hole & a warforged...

[Gruftzwerg]

how a about a spell?

Hoard Gullet (dragon magic)

(Transmutation)
Level: Sorcerer 1, Wizard 1,
Components: V, S,
Casting Time: 1 standard action
Range: Personal
Target: You
Duration: 1 hour/level

Does give you the ability to swallow things into an extra-dimensional space in your body.

edit: Kobolds can select this as SLA for their Draconic Rite of Passage ability.

[Morof Stonehands]

It’s a start, thank everyone!

[Paragon]

The Hoardstealer PrC has Deep Pockets ability at level 3 that lets you turn any pocket into a bag of holding.

[Jervis]

Probably not what you’re looking for but a Sha’ir has a Gen familiar that can brings items back and forth from a place in the elemental planes via its at will planeshift. Also it can carry a bag of holding

[GeoffWatson]

Astral Dreadnought

[MornShine]

Mercane (https://www.d20srd.org/srd/epic/monsters/mercane.htm) is what you're looking for.

[Morof Stonehands]

Thanks everyone, good ideas!

[Dalmosh]

Dalmosh of the Infinite Maws from MMV has an entire demiplane in his stomach

[MaxiDuRaritry]

There're the Packrat (or Pack Rat) feats from Dragon #354, PF (https://www.d20pfsrd.com/feats/general-feats/pack-rat/), and Starjammer (https://www.starjammersrd.com/feats/general-feats-3pp/pack-rat/).

The latter two are the same one, barring prereqs, and they differ from the one in Dragon in quite a few ways. They could be fluffed as a personal extradimensional space, albeit with limitations.

[Telok]

If I recall the etherial filcher has a lair on the etherial plane, that might sort of qualify.

Also the bag of devouring got a creature writeup in some dragon mag a long long time ago. Basically each bag was one "mouth" of a big extradimensional stomach with lots of mouths/bags.

[Fouredged Sword]

A large enough creature to have a 6ft "flat" section inside their stomach could have a portable hole deployed inside, expanding their internal space considerably.

Stomachs are flexible, so you just need a large enough stomach space to flatten one 6ft segment safely and deploy the portable hole. It should work for most creatures with the swallow whole ability.

[Crichton]

A large enough creature to have a 6ft "flat" section inside their stomach could have a portable hole deployed inside, expanding their internal space considerably.

Stomachs are flexible, so you just need a large enough stomach space to flatten one 6ft segment safely and deploy the portable hole. It should work for most creatures with the swallow whole ability.

Or a Dimensional Pocket - A magic item originally made for Beholders - Dragon Magazine #313 pg 56.

[MaxiDuRaritry]

You can purchase or create a 'possum pouch (Complete Adventurer) and add on a handy haversack enhancement, if you want. Or you could do something like this (https://forums.giantitp.com/showthread.php?177889-Brainstorm-for-Psionic-Tricks-Tactics-and-Combos-Handbook&p=23285432&viewfull=1#post23285432), although if the main thing you're after is the storage space, you don't have to go with a psychoactive skin of proteus. You can either choose a different psychoactive skin to use, or avoid using one at all and just go with the illithid humanoid skin graft with the other enhancements.