"Nyx" was an experimental B.O.W. that U.S.S. member Rodriguez attempted to steal from Raccoon City.
History
Very little is known about the actual origins and creation of Nyx. At some point in September 1998, Nyx was imported into Raccoon City from Umbrella Europe for data collection and stored at a cargo dock which was under the watch of Tommy Nielson. Sometime during the biohazard outbreak in the city, the specimen was stolen by U.S.S. member Rodriguez, who transported Nyx's container via helicopter in a bid to get it out of the city and presumably into other hands. His efforts were a failure as Umbrella Headquarters had caught wind of his betrayal and sent Tommy Nielson and a U.B.C.S. team to recover Nyx. 1 After a near-hit from a missile fired by Tommy towards Rodriguez's helicopter, the creature, stored in a crate, fell onto the Raccoon City highway where it quickly broke free and absorbed the entire U.B.C.S. team as well as the Tyrant R before adopting a humanoid form.
After engaging a group of survivors in battle, Nyx was ultimately defeated and it began to break down, signifying its death.
Attributes
In its initial form, Nyx is a sentient being capable of utilizing tentacles to kill and ensnare prey, which it then merges with itself. After it manages to merge with enough organic material, it takes on a large, somewhat humanoid form. Here, it is almost invulnerable to conventional weapons. At most, it can only be weakened. Nyx did however have a weak point, a large purple organ hidden inside its body cavity. After receiving enough damage, Nyx would fall down and expose this weak spot which was exploited by a group of survivors.
Etymology
Nyx gains its namesake from Greek mythology, as the Goddess of Night.