Ectoplasm is a biochemical radiation and/or spiritual energy transfixed to certain magical beings such as Ghosts and invisible beings. The ectoplasm is exteriorized and released from within the beings' cell cytoplasm. Over time, ectoplasm can also manifest as a result of psychic phenomena and hauntings.
The demon known as Troxa is an invisible being who's ectoplasmic biochemistry renders him sensitive to cold; in cooler temperatures, the ectoplasm manifests itself causing Troxa to become partially visible in spirit form.