Corrupture (CR 9)

Huge Ooze (Aquatic)
Alignment: Always neutral
Initiative: -5(Dex); Senses: blind, blindsight 60 ft., and Listen -5

AC: 3 (-2 size, -5 Dex), touch 3, flat-footed 8
Hit Dice: 11d10+99 (159 hp); DR: 5/-
Fort +12, Ref +-2, Will +-2
Speed: 20 ft., Climb 20 ft., and Swim 20 ft.
Space: 15 ft.; Reach 10 ft.
Base Attack +8; Grapple +26
Attack: Melee: slam +16 (2d6+15 plus 2d6 acid)
Special Attacks/Actions: acid burst
Attack Options: acid sheath, trample 2d6+15 plus 2d6 acid
Abilities: Str 31, Dex 1, Con 29, Int -, Wis 1, Cha 1
Special Abilities: Immune: acid, gaze attacks, illusions, visual effects; ooze immunities; SR 18
Special Qualities: amphibious, ooze traits
Skills: Climb +18, Listen -5, and Swim +18
Advancement: 12-22 HD (Huge); 23-33 HD (Gargantuan)
Climate/Terrain: Any sullied environment
Organization: None
Treasure/Possessions: 50% chance of goods/magic items (stone or metallic only), 1/10 standard coin.

Source: Monster Manual IV

Acid Sheath (Ex): A corrupture's body produces corrosive slime. Any creature that strikes or touches a corrupture with its body, or that grapples a corrupture, automatically takes 2d6 points of acid damage. A creature takes damage from this ability only once per turn.

Trample (Ex): Reflex DC 25 half. The save DC is Strength-based.

Acid Burst (Ex): A corrupture can activate an acid burst as a standard action. Any creature within 20 feet must succeed on a DC 24 Reflex save or take 6d6 points of acid damage. A successful save results in half damage. The save DC is Constitution-based.

Amphibious (Ex): A corrupture can survive indefinitely on land or underwater.

Skills: A corrupture has a +8 racial bonus on Climb checks and can always choose to take 10 on Climb checks, even if rushed or threatened. In addition, it has a +8 racial bonus on any Swim check to perform some special action or avoid a hazard. It can always choose to take 10 on a Swim check, even if distracted or endangered. It can use the run action while swimming, provided it swims in a straight line.

Disgusting bags of acid-filled flesh, corruptures result from the warping of nature. They hunger for meat and mindlessly attack living things even as they dissolve the environment that supports their prey.

Aquatic Subtype

Creatures with the aquatic subtype always have swim speeds and thus can move in water without making Swim checks. An aquatic creature can breathe underwater. It cannot also breathe air unless it has the amphibious special quality.