This chapter explores the essential features of Twelver Shī‘ī eschatology in the light of ‘eschatological unity.’ Central to this tradition is the figure of the Twelfth Imām, Muḥammad al-Mahdī, whose concealed state (ghayba) and anticipated reappearance (ẓuhūr) form the cornerstone of Shī‘ī hope in divine justice and ultimate reconciliation. Particular attention is given to the expected joint Parousia of the Mahdī with Jesus, envisioned as a potential horizon of convergence with Christian eschatological belief. The Imām’s role as a bridge between the visible and invisible realms establishes Him as a theological figure uniting time and eternity, exoterism and esoterism, creation and the Divine. The chapter examines core Shī‘ī concepts such as walāya/wilāya (divine guidance, closeness, and relationship among the believers), intiẓār (expectation), raj‘a (return), and qiyāma (resurrection), highlighting their theological richness when viewed through the lens of unity. It also underscores the internal unity of the ahl al-bayt, the Prophet Muḥammad’s family, and of the fundamental dimensions of Mahdology, encouraging a more integrated reading of the Mahdī’s identity and His two occultations. Approaching these themes from a Christian perspective, the chapter adopts an empathetic tone, seeking genuine common ground while preserving doctrinal distinctions. Drawing on both classical sources and contemporary English-language scholarship, it fosters deeper mutual understanding between Catholicism and Shī‘a. Ultimately, the Mahdī’s eschatological mission reflects the Catholic emphasis on the Parousia of Christ, offering fertile ground for shared reflection on hope, divine justice, and cosmic restoration in the presence of the One God.