  We consider the case of axion-like particles (ALPs) during inflation. When
coupled to a non-Abelian gauge sector via a Chern-Simons term, ALPs support an
intriguing, testable, phenomenology with very distinctive features including
chiral primordial gravitational waves. For sufficiently small values of the
gauge vev and coupling, scalar perturbations in the gauge sector exhibit a
known instability. We harness the power of such instability for primordial
black hole (PBH) generation. In the case of an axion-inflaton, one is
dynamically driven into a strong-backreaction regime that crosses the
instability band thereby sourcing a peaked scalar spectrum leading to PBH
production and the related scalar-induced gravitational waves. Remarkably, this
dynamics is largely insensitive to the initial conditions and the shape of the
potential, highlighting the universal nature of the sourcing mechanism. In the
case of spectator ALPs one can identify the parameter space that sets off the
strong backreaction regime and the ensuing features. We show that spectator ALP
models may also access the scalar instability region without triggering strong
backreaction.
