The fourth moon of the planet Yavin houses the temples and ruined buildings of the now-vanished Massassi race, and once served as the primary base for the Rebel Alliance. The moon is covered with a wild, largely unexplored jungle composed of towering Massassi trees.

Over four thousand years ago the dark Sith magician Naga Sadow, under a death sentence from the current Sith Lord, fled to Yavin 4 with his followers where he could practice his Dark Side alchemy in peace. Sadow hid his starship and his alchemic equipment beneath the Sith Temple of Fire. Sadow's alchemy helped create many monsters, including a warrior species called the Massassi designed to guard Sadow's Yavin 4 legacy. The Massassi, the mutated descendants of the ancient Sith, gradually devolved into a primitive but dangerous people, using the Dark Side to augment their archaic weapons. When the Dark Jedi Exar Kun arrived on Yavin 4, he enslaved the Massassi and had them construct new temples as focal points for Sith power. When a united group of Jedi tried to stop him, the resulting battle caused the destruction of most of the moon's jungles and the deaths of the remaining Massassi and Kun was forced to trap his spirit within the temples in order to survive. Thousands of years later, the Alliance constructed its primary base within the abandoned temples. The first Imperial Death Star was destroyed (in what is now referred to as the Battle of Yavin) as the station attempted to fire its superlaser on Yavin 4. During the fighting, an Imperial pilot named Qorl crashed his damaged TIE in the moon's jungles and fruitlessly awaited rescue. The Rebel base was abandoned following the battle, but the Great Temple was used eleven years later as the location of Luke Skywalker's Jedi academy.

The pyramidal Great Temple lies between two broad rivers and lies near the ruins of the Palace of the Woolamander. The top of the Temple houses an observation deck, and below that is the vast grand audience chamber. Below the chamber are housing levels, and the ground level contains the Communications Center, common rooms, and the Alliance's former War Room. The Temple's hangars are located underground. Yavin 4's flora includes nebula orchids, feather ferns, and blueleaf shrub. Indigenous life in Yavin 4's jungles include the social (and edible) woolamanders, mucous salamanders, purple jumping spiders, piranha beetles, lizard crabs, whisper birds, fur-covered runyips, crystal snakes, stump lizards, ravenous stintarils, a six-legged, tusked beast with tentacled eyes, and flying, two- headed reptiles created during the time of Exar Kun.

source: dunesea