Why is Lyxal so Lyxal?
After being spawned by interspacial imps, the Lyxal have been raiding civilization on and off since the dawn of time. A few hundred years ago Lyxal were even a major player in human culture, by far the most populous species that inhabited most of Earth. Some of their writing and art is still visible in many places, and they had plenty of technology at their disposal before they began to go extinct. Scientists are still trying to determine why Lyxal went extinct (perhaps climate change or over-hunting) but some think that it may be related to them being too successful or too dangerous for the humans to successfully keep them in check.
Why did Lyxal develop the ability to "Link" with other beings?
When a Lyxal worm climbs into another person or another creature's body it makes multiple copies of itself across the host's body, effectively erasing all memory save one copy, which takes up residence in the brain. The current consensus is that this behavior is due to a genetic defect in which the original worm successfully passes on its genome but is interrupted in the process of copying its genome onto the other worms. The worm that is left behind looks for another host like itself, and connects with it.
The process of "Linking" can be initiated by either party, but it's a very brief process and both parties must be willing participants. The first time a Lyxal attempts to Link with another individual, it will appear to be a bit disoriented, but otherwise healthy. After the first "Link", Lyxal will not try to Link again unless they feel their partner has been affected by something that they cannot overcome alone.
Why does Lyxal seem to have so many different types?
Like other lycanthropes, each Lyxal species has its own abilities and strengths. The variety of Lyxal species is due to differences in chromosome structure, meaning that some species can only be born when they have particular chromosomes. In addition, members of different species have different abilities and weaknesses, and can only Link with members of their own species. The most common species are the ones that appear in most humanoid societies: the Mephits (the most intelligent), the Owls (the fastest), the Snakes (the stealthiest) and the Rats (the most numerous).