The alchemical adept seems always to have carried out his work in the context of a relationship with a partner of the opposite sex, usually an inner figure but sometimes with a real person, referred to as soror mystica or mystical sister
Samuels establishes the soror mystica as the alchemical adept’s opposite-sex partner — inner anima or outer patient — and maps this dyad onto the analyst-analysand relationship as its psychological equivalent.
, Jung and the Post-Jungians, 1985thesis