  The hypothesis that Dark Matter is one electroweak multiplet leads to
predictive candidates with multi-TeV masses that can form electroweak bound
states. Bound states with the same quantum numbers as electroweak vectors are
found to be especially interesting, as they can be produced resonantly with
large cross sections at lepton colliders. Such bound states exist e.g. if DM is
an automatically stable fermionic weak 5-plet with mass $M \approx$ 14 TeV such
that the DM abundance is reproduced thermally. In this model, a muon collider
could resolve three such bound states. Production rates are so large that
details of DM spectroscopy can be probed with larger statistics: we compute the
characteristic pattern of single and multiple $\gamma$ lines.
