When SIVA, a virus and nanotechnology capable of self-replication and self-assembly, is discovered by the Fallen Splicers, after breaching the Wall that surrounds Earth's last safe city, it begins to consume the Cosmodrome, and even the Moon.

When two Guardians at the Tower intercept an unexpected message from Lord Saladin, they embark on a mission to investigate an observatory in the mountains, where they first encounter SIVA.

And after learning about SIVA and of its lethality, the two Guardians gather their Fireteam to learn more about SIVA and wipe its threats across the Plaguelands, thanks to the Devil Splicers.

And eventually SIVA leads a Guardian into an inevitable fall that consumes…~