Aballin (CR 4)

Large Ooze
Alignment: Always neutral
Initiative: +1 (Dex); Senses: blindsight

AC: 10 (-1 size, +1 Dex), touch 10, flat-footed 9
Hit Dice: 3d10+21 (37 hp); DR: 5/magic
Fort +3, Ref +2, Will +0
Speed: 20 ft., swim 40 ft.
Space: 10 ft./10 ft.
Base Attack +2; Grapple +11
Attack: Slam +6 melee (1d8+7 plus drown)
Special Attacks/Actions: Drown
Abilities: Str 21, Dex 13, Con 14, Int -, Wis 9, Cha 6
Special Qualities: immunities, passive stare, vulnerable to water-affecting spells
Feats: -
Skills: -
Advancement: 4-5 HD (Large); 6-9 HD (Huge)
Climate/Terrain: Warm and temperate land and underground
Organization: Solitary
Treasure/Possessions: None

Source: Monster Compendium: Monsters of Faerûn

Drown: The first victim hit by an aballin's pseudopods must make an opposed grapple check with the aballin (the monster's bonus on this check is +11). If the aballin wins this check, it draws the victim into its fluid body. The victim is at risk of drowning (see Drowning). Because the aballin is composed of acid, not water, spells such as water breathing offer no help in surviving the effect of drowning in their fluids.

A trapped victim can attack the aballin or make additional grapple checks to escape its grasp. The character cannot cast spells with a verbal component or use any other item or ability that requires speech. If other characters use edged weapons to attack the aballin while it is holding a victim, those attacks have a 25% chance of hitting the trapped character, and they do no harm to the aballin.

While holding a victim, the aballin continues to attack with its pseudopods, dealing slam damage to other characters.

Immunities (Ex): Aballins suffer no damage from energy attacks involving fire, cold, or electricity. As noted above, slashing or piercing weapon attacks have a 25% chance of striking a character trapped within an aballin, but they do no harm to the aballin itself. Only bludgeoning weapons can harm the creature (and then only if they overcome its damage reduction).

Passive State: In its passive state, an aballin cannot be harmed by any attacks that would not affect a normal pool of water.

Vulnerable to Water-Affecting Spells (Ex): A transmute water to dust spell forces an aballin to make a Fortitude save (the DC is determined by the attributes of the caster) or perish. A lower water spell forces an aballin to release a trapped character if it fails a Fortitude save.

Aballins lie passively, masquerading as puddles, small ponds, fountains, or cavern pools, indistinguishable from fresh water until a potential victim approaches. When they sense prey nearby, they alter their structure, becoming a 10-foot-tall column of living fluid and lashing out with gelatinous pseudopods at their opponents.