It is not known how Nebrox came to be a slave. He had already been put up for auction once and was scheduled to be killed should he not be sold after a second auction. He shared a cell with Avon and did a deal where the pair would escape together if he could retrieve Avon's teleport bracelet.
A kind and sympathetic old man, Nebrox's attempts to console Piri led to his demise. When Piri didn't respond to some of his references to slave life on Domo, she became concerned that he might realise she was in reality Cancer, and had never been a slave there. She killed him using a venomous crab.