  In this article, we study the hierarchical structure of metastability in the
reversible inclusion process. We fully characterize the third time scale of
metastability subject to any underlying geometry of the system and prove that
this is the last time scale. We also demonstrate that there are no other
meaningful time scales except the three identified ones. This work completes
the verification of the conjecture made in [7] which was partially resolved on
the first time scale in [7] and on the second time scale in [25]. Main tools
are potential-theoretic approach and martingale approach to metastability; we
thoroughly investigate the highly-complicated energy landscape of the system to
construct suitable test objects to provide sharp asymptotics on capacities.
