Hormondan

Hormondan is a fictional element appearing in DC Comics, primarily associated with the planet Daxam and its inhabitants. It is a rare and highly potent substance that is toxic to Kryptonians, rendering them vulnerable and eventually fatal if exposed. While Daxamites themselves are immune to its effects, it serves as a significant weakness for Superman and other Kryptonians who have settled on Daxam.

The element's properties were established to explain why Kryptonians like Lar Gand (Mon-El) and other Daxamites could survive on a planet like Daxam, which is orbited by a yellow sun similar to Krypton's. Unlike Kryptonians, Daxamites are physiologically different, and their interaction with the yellow sun's radiation is not enhanced but rather rendered incompatible with lead. Hormondan's presence, in conjunction with the yellow sun, creates a deadly environment for Kryptonians.

The discovery and understanding of Hormondan have been crucial plot points in various Superman and Legion of Super-Heroes storylines. Treatments and countermeasures have been developed to protect Kryptonians from its effects, often involving lead shielding or specialized medical interventions. The vulnerability to Hormondan has been a recurring challenge for characters like Mon-El, who has had to contend with its debilitating influence throughout his life. Its existence highlights the complex and often dangerous nature of interstellar environments and the unique biological vulnerabilities of different alien species.