The paper presents an ontological conceptualization of the phenomenon of extremity, which is considered in the context of personality transformation in the trans-ordinary world. Methodological principles and scientific logic of conceptualization are proposed and specified in the following concepts: the experience of being and non-being, personality work, meaning and behavioral personality work, positive and negative extremity, the meaning of life and the meaning of death, the nature of the construction of psychological effects of extremity — psychic trauma and personal transformation.