Doctor Phosphorus

In-universe accounts present Alexander James Sartorius as a scientist whose exposure to irradiated material during a nuclear plant meltdown altered him: fictional descriptions state sand irradiated in the meltdown chemically changed him (described in continuity as driven up the periodic table from silicon to phosphorus). This transformation left him no longer wholly human and took place in Detective Comics #469 (May 1977) and subsequent storylines; later continuities and reboots reprise or modify the origin (including scenes tied to nuclear equipment and reactor accidents).

Across comics and animated adaptations he appears as a radiative, burning figure whose skin blisters or 'burns at any contact' and whose skeleton can be seen through flesh (descriptions explicitly note his skeleton showing through like an x-ray). Cadmus scientists in later stories report that his organs have been replaced by energy; adaptations often depict him as a phosphorescent, skeletal, fiery humanoid.

Sources describe him manipulating radiation to produce burning skin, toxic fume emissions, and other thermal/radiative effects. He is portrayed as producing an apparently endless internal source of energy and—after selling his soul to the demon Neron during the Underworld Unleashed event—gains increased control over his powers including temperature regulation (allowing him to wear ordinary clothing without it bursting into flame). He uses these abilities for criminal plots (poisoning water supplies, violent assaults, kidnapping, assassination-for-hire) and can be violent and unstable after trauma in some narratives.