Pope Francis first used the geometrical metaphor of a "polyhedron" in Evangelii Gaudium to address the tension between the universal Church and local churches, illustrating how unity can embrace diversity without collapsing into uniformity or reducing the whole to individual particularities. The same constitutive dynamic can be observed in the principle of co-responsibility articulated in the Synod on Synodality, where all baptized members have equal dignity and a shared but differentiated responsibility for the Church's mission. A reception of this co-responsibility, particularly in the topic of authority and participation, has led to the proposal of an "all ministerial Church" that seems to advance the democratization of ministerial functions as a solution to power asymmetry and abuse of clerical authority, thereby suppressing distinctions in charism, competence, and ministries. This paper contends that authentic co-responsibility promotes the participation of all but defers to "fullness in distinction" and not equality of roles. It reads this principle by taking its impetus for transformation from the image of a polyhedron that integrates "faces" in all shapes and sizes into one unified whole without flattening their differences. A polyhedric ecclesiology illustrates the coexistence of unity and differentiation, where each member ("face") is a full subject with agency while remaining in synergy with other members. The paper hopes to develop the polyhedron as an ecclesiological metaphor and demonstrate its theological innovation as well as praxiological implications in ongoing debates about ecclesial authority and lay participation. Similarly, it critically examines the principle of co-responsibility that motivates participation at all levels, unveiling its promises and pitfalls.