Lots of weird stuff. He can infuse it into himself or into things around him as a power boost or to control it, he can make auras around himself or in an area from it, or just use it to attack or curse someone. Different deaths create different ectoplasm, which change his powers to have a variety of strange effects. For instance, an attack using Cold Wind ectoplasm, harvested from a death from exposure or a sky burial, is an icy attack that can inflict frostbite.