Studies on Gregory of Nyssa are flourishing. In this highly valuable bibliography, two areas stand out: mysticism and eschatology. The former has also been at the centre of a lively controversy, concerning the possibility that Gregory could be described as the actual initiator of mysticism. Eschatology, on its part, has received particular attention, especially in the areas of epektasis and apokatastasis. But these dimensions are connected, as shown by Gregory's Commentary on the Song of Songs, a mystical text par excellence, which offers numerous eschatological insights, which this volume tries to present. The issue is all the more interesting in that Gregory's eschatology is marked by a hermeneutical tension which is reflected in a dichotomy present in the studies devoted to it. Clearly, Gregory has been inspired by the apokatastasis of Origen, but for him, as for the Alexandrian, is it possible to speak of a universal salvation? If the human being is simply a soul which has to be restored to its initial state, what is the value of its history? And the body? And freedom? These questions seem to be linked to the tension between the'circular'dimension of apokatastasis and the'linear'dynamic of epektasis. This is approached through the lens of Christology and ontology, two areas which, in the context of Nyssa studies as a whole, are among the least studied. Therefore, the chapters of the book are aimed at covering the themes in such a way as to reveal the profound relationships between the two foci of theological reflection on the mystery of Christ: on the one hand, the Christological focus proper, on the other, the ontology which emerges from Christological and Trinitarian considerations. Thus, we shall be able to identify the influences and relations, intrinsic and systematic, between the thought about being, the protology and the eschatology, of classical origin, and the thought about Christ in which the divine and the human are united in and through history. This volume, therefore, is arranged in three main parts. The first, most fundamental, approximates to the question of the point of view of eschatology itself, seeking to indicate the importance of mysticism in its development. The second part of the volume is devoted precisely to Gregory's Commentary on the Song of Songs, where the eschatological dimension is clearly highlighted. The third and last part of the volume is devoted to the apokatastasis. Here the different, even contrasting positions, are presented, providing, simultaneously, some tools which could assist a deeper penetration into the tensions of eschatology through the mystical perspective which is characteristic of the Commentary on the Song of Songs. In particular, the Christological and ontological elements linked to epektasis seem to promise a greater immersion into Gregory's eschatology and appreciation of its theological significance, not despite its tensions but precisely by means of them.