Symbiotes are a powerful but largely benevolent and intelligent species of lifeform. Their name is their description : They latch onto creatures and parasitically drain them of a variety of nutrients, in exchange for one or two benefits. These benefits are incredible and wonderful, but it's customary for the symbiote to downplay them (and sensible too, if the creature is to be left alone by the populace).
The symbiote's normal form is that of a human of slender shape. This is the second easiest form they can adopt. They have the shape of a male or female, but despite having bulges in the right places they don't normally exhibit breasts or genetalia. It's as if their whole skin was a thin bodysuit, giving them the right shape but 'hiding' everything. They have the appearance of being freshly born, despite having adult bodies - their skin is wonderfully smooth and free of any flaws, and they have a cute wide-eyed look. They are normally beautiful / handsome. However, their teeth are long, curved and carnivorous, and they have a lengthy, snakelike black tongue. Their eyes are the slit pupilled reptilian type. They have slender, prehensile skinny tails that reach to their feet. They usually appear to have hair - tightly bound into ponytails, arranged into dreadlocks of similar. Actually, each deadlock or ponytail strand is a tentacle, with the texture of hair. These sometimes move by themselves, which can be unsettling. Their skin is always covered with moisture and glitters in soft but strange silvery patterns. This is the symbiotes' stereotypical appearance. Shapeshifting aside, this form varies slightly according to how their parents looked, or what creature they were before being transformed into a symbiote (a popular alternative way of reproducing the species).
If symbiotes are sexually aroused, their bodies instinctively grow the parts that were lacking before - plump breasts, and perfect, sexy mating gear. If they must, and are quick, they can hide this with their natural shapeshifting ability. Whilst mating like this is fine, they will find it hard to resist _really_ using their shapechanging powers. They can grow tentacles of any size and shape easily, to increase pleasure. They can add genitalia of either sex. They can burrow into a victim without causing pain or bodily damage, and pleasure him from the inside, mix him with the parasite's own flesh and share sensations. They can transform a victim they have contact with as easily as they can transform themselves.
If a symbiote is completely relaxed, or comatose (deeper than merely asleep), he will eventually slip into his natural form, the easiest form they can adopt - a giant, greyish, slimy worm, about the size of a human arm. Faceless, sluggish and devoid of any features, symbiotes naturally don't like to look like this in company. It's also when they are at their weakest and most defenceless, due to their size and slowness. If they become a worm in company it shows they trust you, or are surrendering (or like a submissive thrill).
The abilities described above are available to even the youngest symbiote. It's common for one to seek a consenting victim and burrow into them, merging their flesh and linking their thoughts together, living inside them for days on end. While in there they get to eat what they need - the symbiote's diet is that of blood, nutrients in the stomach, sexual fluids and similar. In return they can heal any disease or remove any parasite they find, as well as heal any wound instantly, or slowly grow back a victim's lost limbs and organs (if he has time before the victim dies).
A symbiote practised with his powers can have even more wide ranging powers. He can eat a victims' heart and build a new one while the victim is living off the symbiotes' own blood circulation (again, this doesn't hurt. The symbiote can somehow part the victim's flesh while sealing blood vessels and nerves. It's cleaner and more bloodless than even the most perfect of operations). He can give the victim an insect carapace, or the body of a giant, or perform any physical modification. In exchange for these enhancements, the parasite gets an expanded menu including any of his victims organs and similar fleshy things, without risking harm to the victim. At this level he can transform his host into a true symbiote. This requires him to place the victim inside himself and merge his genetic structure with that of his victim's. (This means the symbiote becomes the 'parent' - they share DNA. The danger here is that during future sexual acts the symbiote and his 'child' may breed, creating inbred offspring. Luckily, the symbiote can merge his partner with another symbiote's sperm or egg cells (stored in a specially prepared sac), creating 'unrelated' offspring that can breed safely). Naturally, the parasite can use all these extra powers on himself as well.
A very experienced symbiote is accordingly very powerful. He can consume the victim's brain, transferring his thoughts to a new one built in it's place. He can destroy his host utterly, and recreate him, keeping hold of his disembodied mind and soul while resculpting an entirely new body. This symbiote gains access to more metaphysical feasts - stray, un-needed thoughts, excess life energy, the odd emotion which can grow back. In return he can mend mental scarring, boost someone's intelligence or bring them back from the dead (though this may require a trip into the afterlife for some literal soul-searching). Again, the parasite can use these extra powers on himself.
A symbiote consumes about the same amount as a human weight for weight, but it must all be flesh or fluids from a living creature (thoughts and emotions available to experienced symbiotes also provide sustenence, but are harder to measure). While the sound of draining and eating the equivalent of several pounds weight from a victim sounds deadly, the parasite just stimulates the victim into overproducing blood, body mass, sexual fluids etc. in response. The latter creates some interesting, if messy, sex scenes. A symbiote host is usually very hungry, ravenously eating for two.
Symbiotes are certainly related to Dragon Suma, Apart from the permanent bonding between dragon and Suma, and the fact a Suma isn;t restricted from full use of her powers by any owner, there are few differences between the two types of creature. Symbiotes are created as offspring from Suma and their dragons, that for some reason didn't become dragons themselves. Others are victims of the perpetual mating from dragon young, their bodies transformed by the experience. Some may even be Suma that have attained individuality (this is unlikely in the extreme. It would be easier for your own heart to attain individuality from your own body).