  Compositionally complex materials have demonstrated extraordinary promise for
structural robustness in extreme environments. Of these, the most commonly
thought of are high entropy alloys, where chemical complexity grants uncommon
combinations of hardness, ductility, and thermal resilience. In contrast to
these metal-metal bonded systems, the addition of ionic and covalent bonding
has led to the discovery of high entropy ceramics. These materials also possess
outstanding structural, thermal, and chemical robustness but with a far greater
variety of functional properties which enable access to continuously
controllable magnetic, electronic, and optical phenomena. In this perspective,
we outline the potential for high entropy ceramics in functional applications
under extreme environments, where intrinsic stability may provide a new path
toward inherently hardened device design. Current works on high entropy
carbides, actinide bearing ceramics, and high entropy oxides are reviewed in
the areas of radiation, high temperature, and corrosion tolerance where the
role of local disorder is shown to create pathways toward self-healing and
structural robustness. In this context, new strategies for creating future
electronic, magnetic, and optical devices to be operated in harsh environments
are outlined.
