• Huge aberration (earth) 15 ft reach, 20 ft with tentacles.
  • 20 RHD of an unimpressive kind (medium BAB, one good save, 2 skills points/HD), and no room for class levels pre-epic.
  • 60 ft speed, burrow 60 ft, climb 60 ft (+ perfect climbing and Xorn movement): very respectable movement rates/methods.
  • +24 natural AC: decent.
  • 4 tentacles 2d6 and bite 2d8: you can hold a mouth-pick weapon, I guess. Otherwise manipulation of tools/objects seems pretty difficult.
  • Constrict/improved grab: nice for any grappler build.
  • Ethereal jolt: Fort save based save or lose, although it doesn't actually finish off enemies.
  • SLAs: at will - calm animals, control plants, cure light wounds, dominate animal, soften earth and stone, stone tell, transmute mud to rock, transmute rock to mud; 5/day - cure serious wounds, true seeing, wall of stone. CL 13. Its a mixed bag there. Control Plants is an 8th level at will, and allows for some limited duration minionmancy, but like so many of their SLAs, is quite situational. Unlimited out of combat healing is OK, but at this level, largely redundant.
  • Darkvision 60 ft, tremorsense 60 ft: decent senses.
  • DR 15 magic and adamantine: also decent.
  • SR 37: very solid SR here.
  • Str +18, Dex +14, Con +16, Int +6, Wis +6, Cha +8: +68, no penalties. No complaints here, although maybe the Str boost could be higher at this level.
  • Small but useful list of racial skills.

Non-humanoid in form, and no manipulative digits. You can speak, which is good. Basically you are a melee bruiser/grappler, with at at will save or vanish attack, a mixed bag of SLAs (most of not very high level), good movement options, decent resilience and decent ability mods.

Can you stand shoulder to shoulder with most 20th level PCs? My gut says no. Yes, you can attack, grapple and send people to the ethereal - but I feel a decently built melee type is going to outpace you on damage output, and possibly versatility as well, once you factor in class options and gear.

I think this would make a decent high level fight for a party, but as a PC? I think it's just a bit lacking. At less HD? Would definitely be harder to call. I think at around 16 HD or so I would be happy to call this a +0.