The Crucible was an ancient Jedi vessel, dating back to the days of the Old Republic. For centuries, it ferried Jedi students from Coruscant to the sacred world of Ilum, where the pupils would undergo the Jedi ritual known as The Gathering. Once a Jedi youngling uncovered a kyber crystal on Ilum, he or she would spend the return trip learning how to assemble a lightsaber. The children would learn from the ancient, wise architect droid, Huyang.
Huyang has served aboard the Crucible for over a thousand years. He has a mental record of every lightsaber ever constructed, and a trove of lightsaber components kept within well-organized cabinets.
The Jedi Order guards the location of Ilum with great secrecy, and by extension, the path of the Crucible. The kyber crystals carried aboard, as well as the wealth of knowledge surrounding lightsaber construction, is priceless.
The lightsaber is the symbol of the Jedi Order, and the Crucible plays an important role in every Jedi's development of his or her weapon. Huyang's enormous inventory of supplies includes a multitude of lightsaber components. The final design of a lightsaber often reflects the personality and spirit of its creator, whether it features a simple grip, a curved approach, is inlaid with the bone of the Cartusion whale, pastillion ore, or black onk.
Ahsoka Tano would help instructing future generations of Jedi, and accompanied one class of bright younglings on their trip to undergo The Gathering. It was during this fateful voyage that the Crucible was attacked by pirates.
Hondo Ohnaka's extensive contacts led him to discover the travel path of the Crucible. Though he had served as an ally to the Jedi in the past, the lure of priceless crystals was too much for this untrustworthy pirate to resist. He and his brigands raided the vessel.