  Assisted annihilation generates thermal sub-GeV dark matter through a novel
annihilation between a pair of dark matter and standard-model-like states,
called the "assister". We show that, depending on the mass hierarchy between
the assister and dark matter, there can be either a suppression or a boost of
the effective cross section. This augmentation enables the possibility of
$\mathcal{O}(100)$ MeV scale dark matter with perturbative coupling that
saturates the relic density estimates while being relatively insulated from
cosmological constraints like big bang nucleosynthesis and cosmic microwave
background.
