This chapter presents experiential features of dissociative phenomena that might have diagnostic, psychotherapeutic, and research implications. The introductory section discusses the case of Eduard a 21-year-old patient who suffers from trace and state forms of dissociative phenomena, in particular depersonalization and derealization. His clinical case shows how these phenomena can cause severe mental distress and how neurology and psychiatry presently deride them at both diagnostic and treatment levels. In Sect. 5.2, we provide a conceptual exegesis of these phenomena in psychiatric literature discussing psychopathological blurs and inconsistencies of this umbrella term and suggesting possible improvements to the epistemology of these phenomena. For that, we draw two representations discussed across the two ensuing sections: Sect. 5.3 Dissociative phenomena through the prism of subjective experience of self (disruptions at physical, pre-reflexive, and narrative experiential levels) and Sect. 5.4 dissociative phenomena through the prism of perceptual experience (perception of reality, perception of pathic dimension, and corporal dimension of the body). These two sections cover an account of the phenomena/experiences that can have the label of "dissociative" and focusing on Eduard's case, their conceptual and phenomenological features. Far more experiences than those presented by Eduard are discussed stressing that various constellations can occur under the topic of dissociative phenomena (and the particularity of Eduard's case). Finally Sect. 5.5 presents a discussion on the clinical implications of these epistemological and phenomenological inputs, including their diagnostic and psychotherapeutic value.