  We use Swampland principles to theoretically disfavor regions of the
parameter space of dark matter and other darkly charged particles that may
exist. The Festina Lente bound, the analogue of the Weak-Gravity conjecture in
de Sitter, places constraints on the mass and charge of dark particles, which
here we show cover regions in parameter space that are currently allowed by
observations. As a consequence, a broad set of new ultra-light particles are in
the Swampland, independently of their cosmic abundance, showing the
complementarity of Quantum Gravity limits with laboratory and astrophysical
studies. In parallel, a Swampland bound on the UV cutoff associated to the
axion giving a St\"{u}ckelberg photon its longitudinal mode translates to a new
constraint on the kinetic mixings and masses of dark photons. This covers part
of the parameter space targeted by upcoming dark-photon direct-detection
experiments. Moreover, it puts astrophysically interesting models in the
Swampland, including freeze-in dark matter through an ultra-light dark photon,
as well as radio models invoked to explain the 21-cm EDGES anomaly.
