The gibbering mouther first appeared in the Monster Manual (version 3.5). This version from Lords of Madnessincorporates errata to that creature and should be considered the official version.
| Hit Dice: | 4d8+24 (42 hp) |
| Initiative: | +1 |
| Speed: | 10 ft. (2 squares), swim 20 ft. |
| Armor Class: | 19 (+1 Dex, +8 natural), touch 11, flat-footed 18 |
| Base Attack/Grapple: | +3/+3 |
| Attack: | Bite +4 melee (1) or spittle +4 ranged touch (1d4 acid plus blindness) |
| Full Attack: | 6 bites +4 melee (1) and spittle +4 ranged touch (1d4 acid plus blindness) |
| Space/Reach: | 5 ft./5 ft. |
| Special Attacks: | Gibbering, spittle, improved grab, blood drain, ground manipulation, swallow whole |
| Special Qualities: | Amorphous, damage reduction 5/bludgeoning, darkvision 60 ft., fluidity 3 |
| Saves: | Fort +7, Ref +4, Will +5 |
| Abilities: | Str 10, Dex 13, Con 22, Int 4, Wis 13, Cha 13 |
| Skills: | Listen +4, Spot +9, Swim +8; racial bonuses |
| Feats: | Lightning Reflexes, Weapon Finesse |
| Environment: | Underground |
| Organization: | Solitary |
| Challenge Rating: | 5 |
| Treasure: | None |
| Alignment: | Usually neutral |
| Advancement: | 5–12 HD (Large) ♊ |
| Level Adjustment: | — |
This unwholesome creature has a body with the form and fluidity of an amoeba. Its surface has the color, but not the consistency, of human flesh. Countless eyes and toothy mouths constantly form and disappear all over the creature, often retreating into its body even as they become apparent.
A gibbering mouther is a horrible creature seemingly drawn from a lunatic’s nightmares. Although not evil, it thirsts after bodily fluids and seems to prefer the blood of intelligent creatures.
Sometimes the arrangement of eyes and mouths on a gibbering mouther’s body a resembles a face, but just as often they have no relationship to one another.
A gibbering mouther is about 3 feet across and 3 to 4 feet high. It weighs about 200 pounds.
Gibbering mouthers can speak Common, but seldom say anything other than gibberish.
A gibbering mouther attacks by shooting out strings of protoplasmic flesh, each ending in one or more eyes and a mouth that bites at the enemy. A mouther can send out a total of six such members in any round.
Blood Drain (Ex): A swallowed opponent automatically takes 1d4 points of Constitution damage each round.
Gibbering (Su): As soon as a mouther spots something edible, it begins a constant gibbering as a free action. All creatures (other than mouthers) within a 60-foot spread must succeed on a DC 13 Will save or be affected as though by a confusion spell for 1d2 rounds. This is a sonic mind-affecting compulsion effect. A creature that successfully saves cannot be affected by the same gibbering mouther’s gibbering for 24 hours. The save DC is Charisma-based.
Ground Manipulation (Su): At will, as a standard action, a gibbering mouther can cause stone and earth in all adjacent squares to become a morass akin to quicksand. Softening earth, sand, or the like takes 1 round, while stone takes 2 rounds. Anyone other than the mouther in that area must take a move-equivalent action to avoid becoming mired (treat as being pinned).
Improved Grab (Ex): To use this ability, a gibbering mouther must hit with a bite attack. It can then attempt to start a grapple as a free action without provoking an attack of opportunity.
Spittle (Ex): As a free action every round, a gibbering mouther fires a stream of spittle at one opponent within 30 feet. The mouther makes a ranged touch attack; if it hits, it deals 1d4 points of acid damage, and the target must succeed on a DC 18 Fortitude save or be blinded for 1d4 rounds. Eyeless creatures are immune to the blinding effect, but are still subject to the acid damage. The save DC is Constitution-based.
Swallow Whole (Ex): A gibbering mouther can attempt to swallow a grappled opponent of Medium or smaller size by making a successful grapple check. (The gibbering mouther doesn’t actually “swallow” the opponent—it engulfs the victim within its amorphous form—but the effect is essentially the same.) Once the victim is inside, the gibbering mouther can use its blood drain ability. A swallowed creature can cut its way out by dealing 5 points of damage to the gibbering mouther (AC 19). Once the creature exits, muscular action closes the hole; another swallowed opponent must cut its own way out. A gibbering mouther’s body can hold 1 Medium, 2 Small, 8 Tiny, 32 Diminutive, or 128 Fine creatures.
(If you are using the variant swallow whole rules, this creature is one that uses the original rule.)
Amorphous (Ex): A gibbering mouther is not subject to critical hits. It cannot be flanked.
Skills: Thanks to their multiple eyes, gibbering mouthers have a +4 racial bonus on Spot checks.
A gibbering mouther has a +8 racial bonus on any Swim check to perform some special action or avoid a hazard. It always can 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.
Source: Monster Manual (version 3.5), page 126.