Continually hearing critical, abusive or threatening voices (auditory verbal hallucinations, AVHs) is a major persisting and disabling symptom of psychotic disorders such as schizophrenia. Current treatments have universally had only modest impact. In preliminary trials, a brief digitally supported treatment, using avatars to recreate AVHs during therapy, has produced some of the largest reductions in AVH severity seen to date. To definitively test the superiority of this innovative treatment, AMETHYST is a randomised controlled trial comparing avatar therapy to current recommended best practice treatment, CBT, for medication-resistant AVHs.