Maraji crystals are an highly addictive narcotic substance that are illegal in the Cardassian Union.
In 2323, Cardassian authorities discovered Maraji crystals in the domiciles of Oralian Way members in the Korto Enclave on Bajor. According to the Cardassian authorities, the Oralians idenfitied Syjin as having supplied them with the substances. Although Maraji crystals were not illegal on Bajor, the fact that the enclaves were considered Cardassian territory meant Syjin was put on trial and faced a Cardassian conservator. After the judge closed the case when Darrah Mace suggested a compromise to stop his friend being turned over to the Cardassians, Els Renora told him she believed the Oralians had been falsely implicated with possessing the Maraji crystals. (TLE - Terok Nor novel: Day of the Vipers)
In 2366, Livara, a Talavian freighter captain who worked for the Romulans as a spy, arrived on Terok Nor and attempted to sell Quark a shipment of maraji crystals. Quark would later claim to Odo that he would not deal in them as the Cardassians disliked them and the Bajorans could not afford them. Odo threatened to hand over Quark to the Obsidian Order if he found out the Ferengi was dealing in maraji crystals. Seven years later, in a hallucination triggered by Odo, it was Thrax who questioned Quark over the crystals. (DS9 episode: "Things Past")