Razulei is a twelve-armed demon and an expert tailor from the Infernal Dimensions. They claimed to be able to weave strands of magic together, which allowed them to create artefacts beyond comparison with the work of any other craftsman.
In the Third Age, following his victory over Zaros, Zamorak came to believe that his inner circle of followers were no more loyal to him than they'd been to the Empty Lord. To deal with this problem, he commissioned Razulei with the creation of a set of robes, imbued with great magical power, but also with cruelty. Razulei returned to him with the robes of subjugation, which he considered to be some of the strongest he would ever make. Zamorak paid Razulei handsomely for his work, and bestowed them upon his inner circle as a great gift. The mages drew power from the robes, but all did so while planning to overthrow, and so found themselves overwhelmed with pain. Perhaps not recognizing that the robes themselves were its source, they drew yet more power from the robes, attempting to abate it, until the strain killed them. Razulei, hearing tell of this much later from a visiting demon, laughed, seeing that Zamorak's fears about his followers' loyalties had proven accurate.
Following Zamorak's banishment during the Gielinorian God Wars, a newer generation of mages took up the robes. Their loyalty to Zamorak enabled them to withstand the pain the robes caused them, and so they were able to siphon magic from the robes without succumbing to them. Razulei was pleased with this, viewing it as proof that Zamorak had finally obtained some loyal followers.
Razulei also created The Rings of Razulei, which build up rage in their owner. The rings at some point came into the possession of the Infernal demon Dagon. Dagon would later trade the rings to the World Guardian, in exchange for providing him with two Hellfire katars.