The Mycon are a race of creatures that nest near the Brahe and Scorpii constallations. While most sentient races (with notable exceptions) are taxonomically animals, the Mycon are fungi. To Humans Mycon living conditions would be most accurately described as "hellish", with temperatures close to the melting point of lead.
Conversations with the Mycon are very difficult, only the Orz could be considered more confusing and even that would be up to debate. The Mycon constantly ramble about Juffo-Wup, the Non and the Void with vaguely religious overtones and often as a complete non sequitur to the topic at hand. They are usually very hostile toward other species, even other Battle Thralls. However they are the only known race to actively seek out the Ur-Quan in order to join The Hierarchy and have always treated that race with respect. It is possible that the Mycon are building up their strength and, in secret, planning the demise of the Ur-Quan.
The Mycon colonize words through agressive terraforming. They launch their Deep Children into the crust of the planet's surface where its tendrils grow, molding the enviroment of the planet to the Mycon's liking with terrible tectonic movement and volcanic activity — it becomes a Shattered World. Mycon prefer warm, living Water Worlds in which to plant these seeds. One victim of this activity was Syra, the Syreen's homeworld.
The Mycon spread the spores of their race through the galaxy with their Podships.
The Umgah can be persuaded to give away a little secret about the Mycon. After capturing one (which, being an inter-thrall conflict, is entirely against the Ur-Quan's rules — so please don't tell) they studied it with their advanced genetic science. It was their conclusion that the Mycon are not at all natural and instead are an advanced, artificial species. They seem to have been created for terraforming purposes, but their "programming" has become corrupted and now their goals are mysterious, if not random. Some theorize that they are of Precursor design, but no evidence exists (other than everything else of equal technical expertise being theirs) to support this.