Megapede (CR 20)

Colossal Vermin
Alignment: Always neutral
Initiative: -2 (Dex); Senses: tremorsense, Listen +10, and Spot +7

AC: 18 (-8 size, -2 Dex, +18 natural), touch 0, flat-footed 18
Hit Dice: 32d8+256 (400 hp); DR: 15/magic adamantine
Fort +26, Ref +8, Will +11
Speed: 80 ft., burrow 20 ft.
Space: 100 ft./10 ft.
Base Attack +24; Grapple +56
Attack: 5 tentacle rakes +32 melee, or bite +32 melee
Full Attack: 5 tentacle rakes +32 melee, or bite +32 melee
Damage: Tentacle rake 2d8+16, bite 4d6+16 plus poison (DC 34)
Special Attacks/Actions: Poison
Abilities: Str 43, Dex 7, Con 27, Int -, Wis 12, Cha 4
Special Qualities: SR 31, vermin traits
Feats: -
Skills: Listen +10 and Spot +7
Advancement: 33-64 HD (Colossal)
Climate/Terrain: Warm desert
Organization: Solitary
Treasure: None

Source: Monster Manual II

True terrors of the desert, megapedes constantly hunt the dunes and sandy plains for food. The desert offers little refuge to creatures fleeing these enormous predators.

A megapede looks like an enormous centipede with a long, segmented body and hundreds of pairs of legs. Its tough, bulbous body is covered with dense orange and brown bristles. The creature's tremendous mandibles twitch involuntarily when it senses prey. A megapede can grow to more than 100 feet in length.