  Searches for Dark Matter at the LHC are commonly described in terms of
simplified models with scalar, pseudo-scalar, vector and axial-vector
mediators. In this work we explore the constraints imposed on such models from
the observed Dark Matter relic abundance. We present these constraints over a
range of mediator masses relevant for the LHC and for future, higher energy
colliders. We additionally compute bounds from a photon line search for the
decay of a pseudo-scalar mediator to di-photons that includes the mediator mass
region near 750 GeV. Finally, we compare cosmological constraints with the
reach of a possible future 100 TeV circular hadron collider, indirect, and
direct detection experiments.
