Traits

[Potion item]: Magic Eclair

A neck that is extended up to one and a half times as long as the leech's own body. 

Leeches with this neck tend to be slender and notably more delicate. Because the length is so unstable, they often have to lie down when feeding to reduce risk of injury.
Necks that are twice as long as the body will almost always result in fatality due to blood being unable to reach the brain, and breeders frequently question how humane the trait is at all. 

[Potion item]: Cursed Keychain

A tail that looks like an object.

Leeches use this tail mutation to bait prey but whether it looks like a slab of meat, a plushie or a big flower- it is still just the leech's tail.

Note: This tail can only resemble one (1) whole inanimate object - it cannot have independently moving, powered, disconnected or jointed parts, and is simply a replica. It may be used to hold things such as liquid or pretty rocks, but the things are not part of the tail.
It is treated as a regular tail would be - any additional tails will require a multi tail upgrade. The upgrade is once per tail.

[Potion item]: Magic Eclair

A tail that is longer than the leech's body.   Visual Reference Guide

While some tails are longer than others, typically a leech's tail is only as long as its body. This odd mutation caused it to grow up to three times the body length. 
Longer tails have been recorded, but they are very easily damaged and tend to have reduced mobility, especially in the wild where it can be caught or attacked easily. 

[Potion item]: Odd Strawberry

The cone hoodie is an elongated hood. Its length can vary from a short point to extending as long as the entire leech! Like the other hooded traits, this hoodie can also be moved up and down off the leech's head.

Unusual wild cases recently have been seen sporting this trait with additional body traits, making it look like the leech has two bodies joined at the head. Experts initially thought it was an odd case of pelt hoodie attaching to the leech's head, but on closer inspection it was a mutated hood trait.
Because of its sudden new appearance, it's thought to be a hidden genome in hooded leeches that triggers growth with an unknown factor.

Note: This can be combined with the Tailmouth to give the cone hood a zipper mouth at the end of it. This does not count as a tail, and tail traits cannot be added to it; the hood tip that pokes out the end should be plain.

[Potion item]: Bone Juice

An outcrop of skeletal structures attached to or emerging through a leech's body.

Leeches don't naturally have bones, therefore leeches with this trait are considered cursed and they are often outcast by other leech monsters. To make it worse, the process of growing bones itself is incredibly painful, and a leech will often have chronic pain due to unnaturally forced nerves and connective tissue around the bone structures.

Note: The bones can be free-standing such as vertical rib shapes, but must still be a fused part of the leech's body; for example, a skull replacing the upper portion of a leech's face is allowed, but a free-hanging skull on a pelt hoodie is not.
Limbs and traits such as hand ears or wings can be combined with this to create skeletal limbs, but it cannot be used to replace parts of a leech that require vital tissue, such as the entire head or neck.

[Potion item]: Harpy Feather

The leech has sprouted feathers all over its body!

Much like fur body, this trait cannot be partial - the leech's entire body must be covered in feathers. However, not all of these feathers are large and gaudy; like a bird they often possess smooth body coating and down, giving them a sleek appearance.

It was thought to be a mutation of fur, but closer analysis revealed it to be a mutation of scales, resulting in soft branching keratin  with a texture much like human hair. Leeches with this trait frequently have skin irritation and will engage in dust baths, scratching, and in some cases where it becomes neurotic, they will stress-pluck themselves bare, leading to a spiral in health as regrowing the feathers is even itchier than having them stay.

Note: Body types cannot be partially applied or mixed outside of an official or legendary capacity. A leech can only have ONE type of body mutation. These are any traits in the trait list with the name 'body' in the title, e.g Fur body, Solid body, Feathered body, etc. OR their official partial variant.

[Potion item]: Snack Sorbet

This  mutation allows for a completely new palette to be added, allowing the leech to swap between the two at will.

Occasionally a leech has been known to develop chromatophores, the same skin color alteration found in octopi and cuttlefish. While not able to sport the wild color and pattern flashes and movement of their cephalopod friends, leeches with color change have been known to flicker rapidly between two different sets of colors.
Despite hopeful breeders, the pattern on the leech's body remains the same.

Note: This is not a free reign ticket to swap out a leech's palette on redesign; it is a trait. The leech's main colors should be its primary image, with the second palette added as an alternative.

Only one additional palette per upgrade can be added; multiple palettes will require multiple items.

[Potion item]: Sham Ham

A mortal injury that should otherwise result in death. This covers open wounds, guts hanging out, impalement, and even decapitation - though in the case of head removal, the head must remain with the leech somewhere.
Refer to this information sheet and its description!

Given that the wounds stay perpetually open, it's likely that it's a mutation tending towards Legendary-tier; a mild telekinesis that instead perpetuates life and function of the main body.

Decapitated leeches must be fed down their exposed neck. Their head cannot be taken too far away or cremated without killing the leech itself.

Note: Healed limb amputations and scars can be used freely, and do not need this trait.

[Potion item]: Natural Soap

A simple elemental mutation which allows a leech to create long-lasting bubbles or foam from its mouth or on its body.

It is recommended to keep children away from Bubble Breath foam as it is created using a somewhat potent mucus, which can be mildly toxic if ingested, and incredibly difficult to clean out of clothing.

[Potion item]: Glass Caps

A trait that only partially presents Glass or Transparent, allowing for significant amounts of the leech's body to remain normal.

Because they are neither fully normal nor fully glass, these leeches have a lot of physical difficulties, including movement. Healing rate is often greatly reduced, especially in the glass portion of the body, as its cells become confused due to the change of texture. Owners must be extremely thorough with their care.

Note: Body types cannot be partially applied or mixed outside of an official or legendary capacity. A leech can only have ONE type of body mutation. These are any traits in the trait list with the name 'body' in the title, e.g Fur body, Solid body, Feathered body, etc. OR their official partial variant.

For Partial Glass, the trait can only use glass OR transparent; not both. Be aware of the visual distinctions between the traits!

[Potion item]: Mange-on-a-String

A mutation in which a leech is covered in patches of fur. Unlike the Fur Body trait, fur doesn't have to cover every inch of the leech's body.

A result of improper breeding for a fur body leech, most often this trait resembles mange and is just as itchy and irritating.
Hopeful breeders attempt to turn the situation around by trying for leeches that look like they have prizewinning haircuts, but the skin irritation that comes with it is more than enough evidence against the practice.

Note: Body types cannot be partially applied or mixed outside of an official or legendary capacity. A leech can only have ONE type of body mutation. These are any traits in the trait list with the name 'body' in the title, e.g Fur body, Solid body, Feathered body, etc. OR their partial variant.

[Item: Bunched Silk]

Drape feelers that are so thin they ripple like fabric. More extreme drapes may take the form of pleats, ruffs, and can even flare out around the paws, giving the appearance of sleeves.

These drapes are luxurious to look at, but incredibly easy to tear and may be indicative of overall fragile skin. Owners should take extreme care to keep their leech from roughhousing, or else they may sustain significant injuries.

Note: Ruffle drapes have the same limitations as normal feelers do, and maintain the same size restrictions as drape feelers.
Bunches of feelers cannot occur from one point in groups of more than three.
Deviations of these (i.e a long line of segmented or pleated feelers, more than two or three points, or more than three bunched feelers) will require the clustered feelers upgrade.

[Potion item]: Glitter Salt

A somewhat unpleasant skin condition that causes the leech to shed particles.

Most of the time the leech's skin dries out or calcifies into rough shapes, sloughing off constantly in a delicate rain of glittery pieces.
It's very pretty to look at, but many disgruntled pet owners often find themselves vacuuming several times a day to manage the mess, and spend a fortune on skin lotions to stop the leech from itching constantly.

[Item: Sail Shell]

A large singular semi-rigid fin that forms in a smooth curve, supported by cartilaginous spokes. It's thought that this is a feeler mutation, due to its consistently simplified shape.
Leeches with this trait have reduced mobility, although those with a sailfin tail are incredibly powerful swimmers for short bursts.

Note: One sail per trait application! Sails on the head do not count as horns.

[Potion item]: Sticky Eggs

Modified feelers with splayed tips that spin a sticky thread, by pressing the spinneret tips onto a surface. It is primarily used to catch prey, but also results in having extremely sticky skin that small objects cling to, often unbeknownst to the leech. These objects then end up being spun into the web.
Spinnerets only occur on the leech's head, upper rump, or tailtip.

Note: This trait is specific to Cave leeches!
Up to three spinneret pairs can be added, one per area.