The Sons of Jormungandr or simply the "Sons" as they call themselves, are a Genestealer Cult that hails from a string of infested space stations that stretch across the Black Nebula.
They worship the resurgent Tyranid Hive Fleet Jormungandr that coils through the Thalassi Sector like some impossibly vast serpent. Using the relative privacy of orbital stations to mask their spread, the Sons prepare for the day when the hour of ascension arrives, and in doing so damns the sector entire as well as reclaiming the Sons' Genestealer Patriarch.
The vector of infection used by the Sons is inspired by the Hive Fleet they worship from afar -- where the Tyranid bio-ships fill hollowed-out asteroids with egg-like Mycetic Spores and hurl them at the target planet, the Sons stow away on bulk Imperial freighters and cargo ships by the thousand.
- Codex: Genestealer Cults (8th Edition), pg. 33
- Codex: Genestealer Cults (7th Edition), pg. 50