Spanish police say they have rescued 15 transgender Brazilians from forced prostitution in the city of Murcia.
The victims were beaten, forced to use and sell drugs, and often kept locked inside a flat, officials say.
They are also said to have been threatened with the use of black magic if they did not comply.
Objects related to the ritual-filled Santería religion were found in the flat. Thirteen suspects were detained for allegedly running the ring.
The authorities say the ring was headed by Brazilian who worked with associates to recruit vulnerable young people in Brazil.
The investigation began after one of the victims filed a report at a Murcia police station.
The victim said their entry into Spain had been arranged in exchange for a large debt, which they then had to pay back via sex work.
Four of the suspects have been detained, while the rest have been released on bail. The investigation continues.