Tartarus Invasion (1)

Within moments, Viper revealed Tartarus' location. Unlike Ashton's belief, the facility was nowhere near Fright City. Hell, the site wasn't even on the mainland like the rest of the facilities. 

Since the experiments conducted there could harm the general populous of the city, it was constructed on an island south of the city.

Tartarus was an island prison, which was later turned into a research facility roughly half a century back. According to Viper, the place was filled with twisted individuals who knew nothing but to kill their target. 

Viper further stated the corpsification gas was tested there before being deployed over Lycania. However, he wasn't sure as he wasn't involved in the project and only heard about it through walls. 

Finally, Viper revealed the reason behind Nirvana's twisted love of conducting experiments, and the reason was not pretty.