They are regarded as being at (one of) the apect of evolution, becoming a species of pure energy that many have regarded as being too complex to complaint, but, for whatever reason, they tend to create forms to use when they are in contact with other beings (it's just as possible for them to use the forms to control them), however, many have called them "A species of psychopaths and sociopaths" sense they're naturally born without empathy and to be self-serving, although not all of them are like this however (90% of total population are as described, but 5% are born with empathy and not (as) self-serving, however, they are about 5% of the population that considered worse then the 90% and the 90% regard them as being psychopaths and sociopaths)
The enter species are hermaphrodites, meaning they have both genders (and thus makes it difficult to exterminate). Once a Wioni reaches adulthood, if he or she (the gender they identify as) can have children by the process of asexual reproduction by mixing and randomizing their genes into a egg and sperm and then became pregnant once the process is compete, the stage of pregnancy lasts for six months and ends when the child is born (though twins and triplets are the most common)
because they are beings of pure energy, the Wioni do not have a defined shape and form, however, they can change their form based upon a process of mental suggestions to make "lesser species" see what they what them to see.
The Chaos Gods of the Warhammer Universe
The Man in the Moon