Rai Kui and her son Vikram Birua were sleeping in their home at Roladih village when her nephew Patar Birua barged into it and slit her throat late Friday night, police said.
Patar also attacked his cousin but he managed to escape with severe injuries in the stomach and hand, police said adding Vikram has been admitted to hospital fro treatment of his injuries.
A police team rushed to the spot and took away the body and arrested Patar, who said he killed his aunt as his father was not keeping well for past several days owing to the black magic practiced by her.