The rakghoul tunnels comprised a network of subterranean passages and caverns situated below the surface of several planets, for instance Alderaan, Tatooine, and Corellia, in which rakghoul infestations had taken root. The presence of these tunnels was a secret until the plague erupted across these planets. The Hyland Organization for Rakghoul Neutralization employed the Spike to penetrate these tunnels, thereby enabling their personnel to fight against the spread of the infection.