  This conference thesis summarizes my presentation at Tartu Tuorla Cosmology
meeting based on a collaborative work with E.Nardi and C.Smarra
\cite{Muursepp:2024mbb}. It is well known that a pseudo-Nambu Goldstone boson
(pNGB) coupled to a confining gauge group obtains a non-zero contribution to
its mass through instanton effects. At non-zero temperature, this manifests in
temperature-dependent mass $m^{2}(T) \propto T^{-n}$. If these particles come
to dominate the energy density of the Universe in the non-relativistic regime
they would accelerate the expansion of the Universe for $n>2$, thus providing a
dark energy (DE) component. In this work, we outline a scenario in which a pNGB
$\phi_{b}$ presently undergoing confinement could realize such a scenario.
Using energetic considerations we find that $\phi_{b}$ alone is not enough to
produce the experimentally observed amount of DE. However, coupling $\phi_{b}$
to the QCD axion $\phi_a$ allows the transfer of energy from the QCD axion to
the pNGB via non-adiabatic level-crossing thus reproducing the observed amount
of dark matter (DM) and DE.
