Shaboath (CR 10)

Large Construct (Cold)
Alignment: Always neutral
Initiative: -1 (Dex)
Languages: Cannot speak

AC: 20 (-1 size, -1 Dex, +12 natural), touch 8, flat-footed 20
Hit Dice: 11d10+30 (60 hp); DR: 10/-
Fort +3, Ref +2, Will +3
Speed: 20 ft., swim 30 ft.
Space: 10 ft./10 ft.
Base Attack +8; Grapple +19
Attack: Slam +14 melee
Full Attack: 4 slams +14 melee
Damage: Slam 2d10+7
Special Attacks/Actions: Engulf, improved grab, wall of ice
Abilities: Str 25, Dex 9, Con -, Int -, Wis 11, Cha 1
Special Qualities: Construct traits, immunity to acid, immunity to cold, vulnerability to fire, watery concealment
Feats: -
Skills: -
Advancement: 12-22 HD (Large); 23-33 HD (Huge)
Climate/Terrain: Underground
Organization: Solitary or gang (2-4)
Treasure/Possessions: None

Source: Lords of Madness

Engulf (Ex): A shaboath can attempt to engulf a grabbed opponent that is equal to or smaller than its size category by making a successful grapple check. Once inside, the opponent takes 2d10+10 points of crushing damage per round. If the opponent cannot breathe water, it must hold its breath or begin to drown. An engulfed creature can escape by making a successful grapple check or Escape Artist check. The amount of time a creature can hold its breath if it takes a standard action is reduced by 1 round. A shaboath can engulf 1 Large creature, 2 Medium creatures, 4 Small creatures, 8 Tiny creatures, 16 Diminutive creatures, or 32 Fine creatures at one time.

Improved Grab (Ex): To use this ability, a shaboath must hit with a slam attack. It can then attempt to start a grapple as a free action without provoking attacks of opportunity. If it wins the grapple check, it can attempt to engulf the target in the following round.

Wall of Ice (Su): A shaboath can generate a wall of ice (as the spell, caster level 20th) once per minute as a standard action that does not provoke attacks of opportunity.

Construct Traits: A shaboath has immunity to poison, sleep effects, paralysis, stunning, disease, death effects, necromancy effects, mind-affecting spells and abilities (charms, compulsions, phantasms, patterns, and morale effects), and any effect that requires a Fortitude save unless it also works on objects or is harmless. It is not subject to extra damage from critical hits, nonlethal damage, ability damage, ability drain, fatigue, exhaustion, or energy drain. It cannot heal damage, but it can be repaired. It has darkvision our to 60 feet and low-light vision.

Watery Concealment (Ex): A shaboath that is completely underwater is difficult to see. Its form constantly shifts and blends with the surrounding water, granting the creature concealment.

Shaboaths are relentless combatants. They are difficult to harm with weaponry and are immune to many spells and energy types; only fire is guaranteed to be effective against them. They attack by forming four large tentacles, which they use to slam any targets in reach (other than aboleths).

Cold Subtype

A creature with the cold subtype has immunity to cold. It has vulnerability to fire, which means it takes half again as much (+50%) damage as normal from fire, regardless of whether a saving throw is allowed, or if the save is a success or failure.