  Motivated by the recently reported diphoton resonance at 750 GeV, we study a
new axion-like bosonic portal model of dark matter physics. When the resonance
particle is identified as the pseudo-scalar mediator, via which the standard
model sector would interact with the dark matter sector, the data from collider
physics would provide profound implications to dark matter phenomenology. In
this paper, we first identify the preferred parameter space of the suggested
portal model from the results of the LHC run with $\sqrt{s}=13$ TeV, and then
we examine the dark matter signature taking into account the data from
cosmic-ray experiments including Fermi-LAT dwarf galaxy $\gamma$-ray search,
HESS $\gamma$-line search, and future CTA diffuse $\gamma$-ray and
$\gamma$-line searches.
