Adega, a planet situated within the Moddell sector, served as the original origin point for lightsaber crystals. Despite Ilum eventually taking over as the main provider of these crystals, the three most prevalent types continued to be known as Adegan crystals.
Adega initially debuted as one of the 200 worlds players could explore in the PC game Star Wars: Rebellion released in 1998. Within the game Rebellion, its encyclopedia states that Adega was "the site of an ancient Jedi stronghold," and it goes on to say that the planet was "the main source of Ilum crystals." It is important to note that in 1998, there was no planet named Adega within Star Wars canon, and the description of Adega in Rebellion bore the closest resemblance to that of Ilum, which was first identified in the Dark Empire endnotes as the origin of Adegan crystals.
According to The Essential Atlas, Adega is located near Ossus, a planet found in the Adega system of the Auril sector within the Outer Rim Territories, suggesting that Adega would logically be within the Adega system. However, The Essential Atlas does not actually list Adega as being a part of the Adega system. In contrast, Rebellion places Adega inside the Moddell sector of the Outer Rim.