n gargantuan animal 

Perception +18; darkvision

Skills Acrobatics +16, Athletics +21

Str +8 Dex +1 Con +5 Int -5 Wis +5 Cha -4

AC  28; Fort +20, Ref +16, Will +18

HP 155

Speed 50 feet, climb 50 feet

Melee [>] mandibles +21 (reach 20 feet), Damage 2d10+12 piercing plus titan centipede venom

Melee [>] foot +19, Damage 2d8+10 bludgeoning

Impaling Critical When a titan centipede scores a critical hit with its mandibles, the target is painfully pierced with barbed spines and bristles, taking 1d6 persistent bleed damage and becoming flat-footed as long as the bleed damage continues.

Titan Centipede Venom (poison) Saving Throw DC 28 Fortitude; Maximum Duration 6 rounds; Stage 1 2d6 poison damage and clumsy 2 (1 round); Stage 2 2d8 poison damage, clumsy 2, and slowed 1 (1 round); Stage 3 2d10 poison damage, clumsy 2, and slowed 2 (1 round)

Trample [>>>] Huge or smaller, foot, DC 28

Undulate [>] The titan centipede Strides up to its Speed or Steps. During this movement, it can pass through spaces as narrow as 10 feet without Squeezing.

Bestiary 2, page 50.