Rakghouls are a living plague‒the manifestation of a highly communicable disease capable of swiftly transforming its victims into twisted, degenerate monsters with predatory instincts. The rakghoul virus can infect hundreds of known species and is most often delivered through a rakghoul's bite; a person attacked by a rakghoul and “lucky” enough to survive typically becomes a rakghoul him- or herself. Some victims resist the virus for days, succumbing to rakghoul instincts while retaining their original bodies.
Different strains of the virus manifest in different breeds of rakghoul‒the smallest and weakest travel in enormous colonies, whereas larger, smarter rakghouls often hunt alone. The virus mutates fastest when infecting new species, and slowest when rakghouls reproduce with other rakghouls.
Before the planet's bombardment, Taris contained its substantial rakghoul population in the undercity. Many specialists believe rakghouls are native to Taris, but rare outbreaks elsewhere in the galaxy suggest the truth is more complicated.