The Demon Moon of Onderon - more commonly known as Dxun - is a green orb of overgrown jungles and many dangers lurking within the shadows of its nearly impenetrable canopy. Its untamed wilds stretch as far as the eye can see, covering the entirety of the moon's surface. Dxun is the largest of Onderon's four lunar companions and perhaps its most notorious in terms of galactic history and significance. It is said that many things are buried beneath its verdant canopy, with some supposedly better left forgotten and lost to the galaxy. Yet, a couple of major landmarks are known to the wider galactic community, such as the ruins of an abandoned Mandalorian Outpost deep within the most inaccessible bowels of the seemingly endless jungle, or the fabled Tomb of Freedon Nadd which houses the remains of Onderon's legendary Sith conqueror and the planet’s first king. Some claim that the ancient mausoleum is still a source of Dark Side energy, a malevolent presence haunting within its walls and halls. Yet, few dare to tread upon this domain of rumoured evil, leaving whatever stirs restlessly within the shadows of the tomb undisturbed.

Onderon and Dxun are uniquely tied together, as the flora and fauna native to the former is equally abundant and thriving on the latter. This is a result of the unusual proximity between Dxun and its parent world, which periodically allows the atmosphere of each to pass through and intertwine with the other. Fearsome flying beasts like the mighty drexl are capable of flying from Onderon to Dxun on such occasions, accidentally or purposefully carrying over seeds and spores from one world to the other. Despite this, Dxun evolved its own collection of various indigenous predators and hunters, such as the all-consuming cannoks, the long-clawed and sharply fanged maalraas, the ravenous thick-scaled boma beasts, or the rare reptilian alpha predators of the jungle called zakkegs, among others. Onderon's lunar companion is also home to parasitic life forms called orbalisks, whose crustacean-like shells are rumoured to be absolutely impenetrable, yet which attach to their host and slowly envelop their entire body. It is without a doubt that Dxun has earned its name as the Demon Moon, for its native wildlife evolved to be unusually and uniquely vicious and predatory.

Dxun has long been tied to the history of Onderon. During the Beast Wars, when the infamous Beast Riders waged war against Onderon's capital city of Iziz, the moon was one of their strongholds and place of breeding for their beasts of war. Later, when the Mandalorians had made their way to Dxun, Mandalore the Ultimate had turned it into his stronghold and a primary staging ground for his attacks that started the Mandalorian Wars of roughly four thousand years ago. The battle that was fought on the moon between the Republic and Mandalorians was one of the bloodiest conflicts of that war, and proved to be a costly victory for the Republic. After the war, Dxun became largely uninhabited by any sentient species save for the occasional clandestine research facility or underworld elements seeking shelter from pursuing authorities. In recent years, Onderon’s Demon Moon has become a proving ground for the Mandalorians of Mandalore, its warriors seeking to test themselves against the claws and fangs of the monsters and beasts that prowl the treacherous jungles of Dxun.