  We study a disordered ensemble of quantum emitters collectively coupled to a
lossless cavity mode. The latter is found to modify the localization properties
of the "dark" eigenstates, which exhibit a character of being localized on
multiple, noncontiguous sites. We denote such states as semi-localized and
characterize them by means of standard localization measures. We show that
those states can very efficiently contribute to coherent energy transport. Our
paper underlines the important role of dark states in systems with strong
light-matter coupling.
