Flail Snail

Flail snails are earth-based creatures that were highly sought out by hunters due to the fact that they produce a number of valuable resources. Their body parts and colorful shells can be used to produce several protective magical items.
Flail snails hadlve between four and six tentacles (typically five) that were kept in constant motion, swaying slowly if the creature is calm or fast if it was agitated.
They possess very colorful scintillating shells that had antimagic properties. These keep growing as the creature ages and could grow clockwise or counter-clockwise.
Flail snails move slowly, consuming everything in their path, including vegetation, rocks, sand, and dirt. They are particularly fond of crystal growths and mineral deposits and take their time to savor them. They are generally completely non-aggressive until threatened.
The slow metabolism of flail snails render them immune to poison, while their thick shells and the wet mucus that covered their bodies render them immune to fire.
This protective mucus is produced by a gland in front of a flail snail's foot. The mucus serves as a protective layer for its skin and as a lubricant for its motion. As it moves, the flail snail leaves a trail of this shimmering material that could be harvested to produce clear or opaque glass.
Like any snails, they are somewhat vulnerable to salt, although their protective mucus provided an effective layer of resistance.
Flail snails are hermaphrodites. They reproduce by going through a complex mating ritual with other flail snails that they meet casually. They exchang love darts in order to initiate the ritual, mated, and then go their separate ways. Later on they lay about a dozen eggs.
A flail snail's shell can emit an extremely bright, multicolored light that makes it difficult for the creature to be physically targeted and that could potentially stun its enemies. The shell also renders it extremely resistant to magic. If the creature is targeted by a magical attack, the shell can either reflect the attack back on the caster or convert the spell energy into a destructive blast of force.
The club-like tentacles of flail snails has tips of hardened skin with several protrusions that could crush wood easily and are the creature's only form of attack. If a tentacle is sufficiently damaged, it would die, but the snail would remain alive and can regrow lost tentacles after a few days, as long as at least one tentacle remained alive.
If all tentacles are killed, the snail retracts into its shell and starts crying out a loud wailing sound for several minutes until it dies or has its tentacles restored, such as through a regenerate spell. The cry of a dying flail snail can potentially attract other monsters to the site.
Flail snails hibernate during winter, except in locations in which the seasons do not affect the availability of food, such as deep underground. They tend to flee from overly bright lights as an instinctual defense mechanism against desiccation by the sun.
An intact shell of a flail snail can sell for up to 5,000 gp, and can be used to produce shields that retained their anti-magic property for one month or more. When this effect fades, the shields could then be converted into spellguard shields. A shell can also be powdered and mixed into a dye in order to craft robes of scintillating colors.
The stomach and liver of a flail snail can be used as ingredients for an elixir of health, which negates the effects of any ingested poison. Its skin and protective mucus can be ground and used as an ingredient to produce potions of fire resistance. The mucus can also be used as an alternative ingredient to produce potions of climbing, but it renders the potions too thick to be ingested quickly.
Some humanoids manage to make a living by trailing flail snails and collecting the shimmering lubricant left in their wake.
Source: https://forgottenrealms.fandom.com/wiki/Flail_snail