  We study scenarios where loop processes give the dominant contributions to
dark matter decay or annihilation despite the presence of tree level channels.
We illustrate this possibility in a specific model where dark matter is part of
a hidden sector that communicates with the Standard Model sector via a heavy
neutrino portal. We explain the underpinning rationale for how loop processes
mediated by the portal neutrinos can parametrically dominate over tree level
decay channels, and demonstrate that this qualitatively changes the indirect
detection signals in positrons, neutrinos, and gamma rays.
