  A preponderance of astrophysical and cosmological evidence indicates that the
universe contains not only visible matter but also dark matter. In order to
suppress the couplings between the dark and visible sectors, a standard
assumption is that these two sectors communicate only through a mediator. In
this paper we make a simple but important observation: if the dark sector
contains multiple components with similar quantum numbers, then this mediator
also generically gives rise to dark-sector decays, with heavier dark components
decaying to lighter components. This in turn can even give rise to relatively
long dark decay chains, with each step of the decay chain also producing
visible matter. The visible byproducts of such mediator-induced decay chains
can therefore serve as a unique signature of such scenarios. In order to
examine this possibility more concretely, we examine a scenario in which a
multi-component dark sector is connected through a mediator to Standard-Model
quarks. We then demonstrate that such a scenario gives rise to multi-jet
collider signatures, and we examine the properties of such jets at both the
parton and detector levels. Within relatively large regions of parameter space,
we find that such multi-jet signatures are not excluded by existing monojet and
multi-jet searches. Such decay cascades therefore represent a potential
discovery route for multi-component dark sectors at current and future
colliders.
