Gibberling (CR 1/3)

Small Monstrous Humanoid
Alignment: Always chaotic neutral
Initiative: +0; Senses: Spot +2

AC: 12 (+1 size, +1 natural), touch 11, flat-footed 12
Hit Dice: 1d8 (4 hp)
Fort +0, Ref +2, Will -2
Speed: 30 ft.
Space: 5 ft./5 ft.
Base Attack +1; Grapple -4
Attack: Bite +2 melee; or dagger +1 melee
Full Attack: Bite +2 melee; or dagger +1 melee
Damage: Bite 1d3; or dagger 1d4
Special Attacks/Actions: Gibber, teamwork
Abilities: Str 10, Dex 10, Con 10, Int 5, Wis 7, Cha 2
Special Qualities: Bunching, immunities, light vulnerability, fire vulnerability
Feats: Weapon Focus (bite)
Skills: Spot +2
Advancement: -
Climate/Terrain: Temperate forest and underground
Organization: Solitary, horde (20-100), or wave (101-500)
Treasure/Possessions: None

Source: Monster Compendium: Monsters of Faerûn

Gibber (Ex): Gibberlings' continual insane muttering and shrieking can unnerve creatures with fewer than 2 HD, requiring them to make a Will save (DC 10) or be shaken. Creatures with 2 or more HD do not have to make a Will save, but all Concentration checks by creatures who can hear gibberlings within 200 feet suffer a -2 penalty. Note that in most circumstances, gibberlings' gibbering prevents them from achieving surprise.

Teamwork (Ex): For every two gibberlings that are grappling a foe, all gibberlings get a +2 competence bonus on attacks against that foe.

Bunching (Ex): Gibberlings swarm over and around each other with ease. Up to three gibberlings can occupy the same 5-foot-by-5-foot space.

Immunities (Ex): Like vermin, gibberlings are immune to all mind-influencing effects, including charms, compulsions, phantasms, and morale effects.

Light Vulnerability (Ex): Daylight, or the daylight spell, affects gibberlings like a slow spell. They get no save against this effect. Being slowed in this fashion does not deter gibberlings from attacking, it just renders them less effective.

Fire Vulnerability (Ex): A gibberling attacked with fire must make a Will save (DC 12) or hang back and refuse to advance the next round. The gibberling can still defend itself, it merely fails to advance or to attack in that one round.

Gibberlings rush opponents en masse and attempt to grapple. The first gibberling rushing a specific foe is likely to be downed by an opportunity attack, but eventually defenders run out of opportunity attacks and the gibberling keep swarming on. As Small creatures, up to eight gibberlings can grapple a single Medium-size creature. Unless stopped by magic or impassable barriers of fire, gibberlings advance relentlessly until they are dead.