  In this work, we investigate a scenario in which heavy Majorana Right-Handed
Neutrinos (RHNs) are in thermal equilibrium with a dark sector with temperature
higher than the Standard Model (SM) thermal bath. Specifically, we consider the
scenario in which thermal Dark Matter (DM) abundance is fixed from the
freeze-out of DM annihilations into RHNs. Due to the inert nature of the RHNs,
we show that it is possible for the two sectors to remain thermally decoupled
by having more than two generations of the RHNs. The hotter temperature implies
higher abundances of DM and RHNs with the following consequences. For
leptogenesis, an enhancement in efficiency up to a factor of 51.6 can be
obtained, though a resonant enhancement of CP violation is still required due
to an upper mass bound of about 4 TeV for the RHNs. For the DM, an enhanced
annihilation cross section up to a factor of 51.6 is required to obtain the
correct DM abundance. This scenario can be probed via indirect detection of DM
annihilating into RHNs, which then decay into $h\,\nu$, $Z\,\nu$ and $W^{\pm}
\ell^{\mp}$ with an enhanced annihilation cross section above the typical
thermal value.
