Shriekers are normally quiet, mindless fungus which are ambulatory. They live in dark places beneath the ground. 

Light within 30-ft or movement within 10-ft will cause them to emit a piercing shriek which lasts for 1-3 melee rounds. This noise has a 50% chance of attracting wandering monsters each round thereafter. 

Purple worms and shambling mounds greatly prize shrieker as food.

Violet fungus growths resemble shriekers, and are usually (75%) encountered with them. The latter are immune to the touch of violet fungi, and the two types of creatures complement each other's existence. Violet fungi favors rotted animal matter to grow upon. 

Each fungus has 1 to 4 branches which it will flail out with if any animal comes within their 1-ft to 4-ft range. The excretion from these branches rots flesh in but one melee round unless a saving throw versus Poison is made or a cure disease is used. 

The branch length of this growth depends upon size. Violet fungi range from 4-ft to 7-ft tall, the smallest having 1-ft branches, the 5-ft sort having 2-ft branches, etc. Any sized growth can have 1 to 4 branches.

Ascomoids are huge puffball-like fungi with very thick, leathery skin.

They move by rolling. At first movement is slow — 3" for one round, 6" the next, then 9", then finally 12"—but they can keep it up for hours without tiring.

Ascomoids attack by rolling into or over opponents. Small and medium-sized opponents are knocked down and must rise during the next round or remain prone.

The creature's surface is covered with numerous pocks which serve as sensory organs. Each pock can also emit a jet of spores. Ascomoids also use their spore jets to attack dangerous enemies. Large opponents or those who have inflicted damage upon the ascomoids will always be attacked by spore jets. 

The stream of spores is about 1 foot in diameter and 30 feet long. Upon striking, the stream puffs into a cloud of variable diameter (5-20). The creature(s) under attack must save vs. Poison or die from infection in its (their) internal systems in 1-4 rounds. Even those saving are blinded and choked to such an extent that they will require 1-4 rounds to recover and rejoin melee. Meanwhile, they are nearly helpless, and all attacks upon them are at +4 with no shield or Dexterity bonuses allowed.

Different types of weapons affect the ascomoid differently. 

Piercing weapons, such as spears over 6 feet long, score double damage. 

Shorter stabbing weapons do damage as if against a small-sized opponent.

Similarly, blunt weapons do not harm ascomoids; slashes and cuts from edged weapons cause only 1 point of damage; and magical attacks, such as magic missiles, fireballs, and lightning, etc., are saved against at +4, and damage is only 50% of normal. (Cold-based attacks are at normal probabilities.) 

As these fungi have no minds by ordinary standards, all spells affecting the brain (charm, ESP, etc.), unless specific to plants, are useless.

Basidironds are multi-stemmed fungoid monsters with woody, leathery bodies of orange color. Their cone-shaped upper portions look much like reversed umbrellas, the interior of which is sooty black.

In combat, these fungoid monsters lash forward with their cone-shaped caps that eject spores. A successful hit inflicts 2-8 points of damage and requires the victim to save vs. Poison or have spores clogging its respiratory tract. The victim can smother from these growths in 2-5 rounds unless a cure disease (or its equivalent) is cast.

Basidironds can also use hallucinatory spores which they emit only when they are standing quietly. The spores from each basidirond form an invisible cloud around it with a 20-35" radius. The spores cause each creature within the basidirond's cloud to save vs. Poison each round or begin hallucinating. 

Hallucination lasts as long as the individual is within the cloud and for 1-4 rounds after leaving it. Typical hallucinatory effects on 1d8 are:

Basidironds have no minds by human standards, so all forms of mental attacks, including charm monster, hold monster, and similar spells, have no effect. 

A cold-based attack will not damage a basidirond but will slow the monster to 50% normal movement and prevent spore attacks.

At any distance greater than 10-ft a gas spore is 90% likely to be mistaken for a beholder. Even at close ranges there is a 25% possibility that the creature will be viewed as the eye tyrant, for a gas spore has a false central eye and rhizome growths atop it which strongly resemble the eye stalks of a beholder. 

If the spore is struck for even one point of damage it will explode, its gaseous contents react violently to air, and every creature within a 20-ft radius takes 6-36 hit points of damage (3-18 if saving throw versus Wands is made). 

If a gas spore makes contact with exposed flesh the spore shoots tiny rhizomes into the living matter and grows throughout the victim's system in but one melee round. The gas spore dies immediately. The victim must get a cure disease within 24 hours or die, sprouting 2-8 gas spores.

The algae-like phycomids resemble fibrous blobs of decomposing, milky-colored matter with capped fungi growing out of them. These fungoid monsters have sensory organs for heat, sound, and vibrations located in several clusters.

They exude a highly alkaline substance when attacking. When phycomids attack, they extrude a tube and discharge the alkaline fluid in small globules that have a range of 7-12 feet. In addition to alkaline damage, the globs which these creatures discharge might also cause victims to serve as hosts for new phycomid growth. If a victim fails to save vs. Poison, the individual will begin to sprout mushroom-like growths in the infected area. This will occur in 5-8 rounds and inflict 5-8 points of damage. The growths will then begin to spread throughout the host body, killing it in 5-8 turns, and turning it into a new phycomid. A cure disease spell will stop the spread through the host.

Phycomids are immune to all forms of mental attacks, including charms, holds, etc. Fire-based attacks are saved against at +4, and damage inflicted is either half-normal or none.

Ustilagor fungi appear to be brain-like growths with coral-like appendages. Although soft and not fast by normal standards, they can scuttle and dart, and this accounts for their relatively high armor class. 

Their attack consists of flicking out ribbon-like tendrils about 3 feet long. A hit inflicts damage due to alkaline fluids and causes the victim to save vs. Poison or suffer additional like damage (2-5 hp) on the following round as the caustic substance affects its body.

Ustilagors have no Intelligence or mind as defined by human standards, so mental attacks do not affect them. (Cf., PLAYERS HANDBOOK, p. 11, Wisdom Table, asterisked paragraph regarding magical attack adjustment.) 

These monsters do, however, have some form of brain, for they have psionic powers. Ustilagors can employ [telepathic] projection to project the following emotions on an individual during a round: hate for associate, distrust of associate, fear of fungi, loathing of area, or uncertainty These projected emotions cause attack, bickering, desertion, or dithering, accordingly. 

Ustilagors also use energy control to protect themselves from spell attacks and the like. 

They attack psionic individuals only by id insinuation (as related to the strongest basic emotions.) Only a psionic blast will affect them in turn.

Brown Mold grows anywhere beneath the surface of the ground. It is light tan to golden brown in color. 

It cannot stand high concentrations of ultraviolet light, but it feeds on radiant energy of most other sorts. 

Where a patch of brown mold grows, the temperature will be below average. If a creature walks within 5-ft of the patch, the mold will begin absorbing its body heat — even from a basically cold blooded creature. Each melee round that a creature is within 5-ft of brown mold, the mold will drain heat equal to 1-8 hit points frost damage for every 10 degrees of body heat over 55 degrees the creature has. Worse still, this mold grows instantaneously from heat, so if a torch, flaming oil, or a fireball is near the patch, it will be able to grow 2, 4, or 8 times its area from the heat fed to it. This growth will be so rapid that on the next melee round it will have spread and be draining any further heat in its new area of growth. Brown mold is not fed by light spells or faerie fire. 

It is affected only by magical cold, and no other magical or non-magical attacks. Ice storms or walls of ice cause it to go dormant for 5-30 turns. A cold wand [wand of frost] or white dragon breath will kill it. 

The growth does not harm creatures which use cold (white dragons, ice toads, or winter wolves.)

Russet Mold. Found only in damp areas underground, this mold is often mistaken for rust at distances greater than 30 feet (70% chance). Russet mold is golden-brown to rust-red in color. Its lumpy texture is similar to cold porridge, and it is covered by short, hair-like growths. These stand upright and constantly waver as if in a gentle breeze.

It is immune to all attacks involving weapons, fire, and cold but is vulnerable to applications of alcohol, acid, and compounds harmful to plants (such as salt). [In this case, the mold has 12-16 hit points per 10 square feet.] It can be killed instantly by casting a cure disease or a continual light upon it. 

Russet mold makes no physical attacks but emits a barely visible cloud of spores within a 3-foot radius; beyond this radius the spores settle to the floor, inert. Also, if the mold is touched it will inject these spores. All creatures passing within 3 feet or touching it will take 5-20 points of damage from the toxicity and must save vs. Poison. Failure to save results in a sickness that will kill in 2-5 turns unless a cure disease is cast.

Any character who dies from touching russet mold will undergo a transformation. The body will first start to sprout new growths of mold from the spores left at contact. Then, when entirely encased in mold, a vegepygmy (q.v.) will rise from the remains. The entire process will take 21-24 hours (1d4+20). A hold plant spell will halt the growth of the mold for the duration of the spell. If the mold grows for more than 1 hour, the victim cannot be recovered except by a wish spell.

Yellow Mold: A more common underground fungus is yellow mold, which is pale yellow to a golden orange in color. 

Any creature which touches this mold is attacked by its enzymes. [These do 1d8 damage to the one touching it.] It also affects wood, albeit more slowly. It does no harm to metals or stone. 

If the substance is contacted roughly, there is a 50% chance per contact that the colony will release spores. These deadly spores shoot out in an asphyxiating cloud, 1" by 1" by 1", originating from the center of impact. Any creature which is within this cloud will die, its lungs filled with yellow mold growth, unless it makes a saving throw versus Poison. A cure disease and a resurrection are necessary within 24 hours to save such victims.

Yellow mold is affected only by fire based attacks — flaming oil, a fire elemental, etc. Continual light will cause it to become dormant for 2-12 turns, but thereafter the mold will grow over the light and obliterate it. [ie. The mold must be the target of the spell although it is treated as an object and does not receive a save.]

When formed into great colonies of at least 300 square feet in area this growth will form a collective intelligence about 1 time in 6. If this should happen the yellow mold will be aware mentally and psionically. It will attack by spore cloud if it senses the presence of other life forms (range of sensing will vary from 10-ft to 60-ft) or psionically if such abilities are used within from 20-ft to 120-ft (random determination of sensing range). If it attacks psionically, it will await the approach of the life form and then loose an attack which is equal to the most powerful form of id insinuation. It cannot be counter-attacked psionically unless a cleric who has the power to telepathically communicate with plants is on hand, for he will be needed to channel such attacks into a form which will affect the vegetable intelligence of the mold colony. Otherwise, the yellow mold must be physically attacked and destroyed. The colony has sufficient power to make from 1 to 10 psionic attacks within as many turns, and after resting for 1-4 days it will thereafter be able to again attack in this manner.

Green slimes are strange plant growths found in subterranean places. Although they cannot move, they slowly grow, feeding on animal, vegetable and metallic substances. 

They are sensitive to vibrations and will often drop upon passing creatures from above.

Green slime will attach itself to living flesh, and in 1-4 melee rounds thereafter turn the creature into green slime (no resurrection possible). 

It eats away wood slowly, consuming but one inch thickness in an hour.

Green slime eats metals quickly, going through plate armor in 3 melee rounds.

It can be scraped off quickly (if the scraper is then discarded), excised, frozen, or burned. 

A cure disease spell kills green slime.

Other forms of attack - including weapons or spell — do it no harm.

Occasionally huge slimes or colonies of dozens have been reported.