  We present a mechanism that addresses the electroweak, the strong CP, and the
flavor hierarchies of the Standard Model (including neutrino masses) in a
unified way. The naturalness of the electroweak scale is solved together with
the strong CP problem by the Nelson-Barr relaxion: the relaxion field is
identified with the pseudo-Nambu-Goldstone boson of an abelian symmetry with no
QCD anomaly. The Nelson-Barr sector generates the "rolling" potential and the
relaxion vacuum expectation value at the stopping point is mapped to the
Cabibbo-Kobayashi-Maskawa phase. An abelian symmetry accounts for the Standard
Model's mass hierarchies and flavor textures through the Froggatt-Nielsen
mechanism. We show how the "backreaction" potential of the relaxion can be
induced by a sterile neutrino sector, without any extra state with electroweak
quantum numbers. The same construction successfully explains neutrino masses
and mixings. The only light field in our construction is the relaxion, which we
call the hierarchion because it is essentially linked to our construct that
accounts for all the Standard Model hierarchies. Given its interplay with
flavor symmetries, the hierarchion can be probed in flavor-violating decays of
the Standard Model fermions, motivating a further experimental effort in
looking for new physics in rare decays of leptons and mesons.
