Crawling Apocalypse (CR 11)

Gargantuan Undead
Alignment: Always lawful evil
Initiative: +4; Senses: darkvision 60 ft., Listen +18, and Spot +19

AC: 30 (-4 size, +24 natural), touch 6, flat-footed 30
Hit Dice: 20d12+100 (230 hp); DR: 5/-
Fort +6, Ref +6, Will +17
Speed: 20 ft., burrow 20 ft.
Space: 20 ft./15 ft. (25 ft. with tentacles)
Base Attack +10; Grapple +34
Attack: Tentacle +18 melee
Full Attack: 2 tentacles +18 melee and 6 arms +13 melee
Damage: Tentacles 2d8+12/19-20 plus mummy rot, arms 1d6+6
Special Attacks/Actions: Despair, mummy rot
Abilities: Str 34, Dex 10, Con -, Int 6, Wis 20, Cha 20
Special Qualities: fast healing 10, undead traits, unholy toughness, vulnerability to fire
Feats: Alertness; Blind-fight; Combat Expertise; Improved Critical (tentacle); Improved Initiative; Improved Trip; Iron Will
Skills: Listen +18 and Spot +19
Advancement: 21-32 HD (Gargantuan); 33-60 HD (Colossal)
Climate/Terrain: Warm deserts
Organization: Solitary
Treasure: Standard

Source: Sandstorm

A horrible nest of withered, desiccated tentacles heaves from the sand. Behind the tentacles is a barrellike body wrapped in centuries-old funeral dressings. Two staring orbs surmount the gargantuan form, promising annihilation.

A few crawling apocalypses yet traverse the trackless sands, self-impelled immortal remnants of ancient wars.

Each crawling apocalypse is actually a war machine created by a race called the marru. Known for their power over the flesh of the living, splinter factions of marru wandered into realms of necromancy, and in their madness to win at any cost, they introduced monstrosities of the sea to mummification and the sea of sand. Too potent to perish with the conclusion of the wars and the eradication of their creators, crawling apocalypses yet patrol ancient perimeters, guarding against intrusion by enemies long vanished.

While some roving weapons of the ancient marru still sometimes rise to the surface and cause desolation, most remaining crawling apocalypses are secreted in ancient weapon depots, well hidden thousands of feet below the desert surface. They have vague memories of their former living existence, thousands of years ago. The memory of their former mastery, and what was taken from them, fuels their violence against all creatures. Some could still respond to command codes devised by the marru, though those codes are most likely all forgotten.