Season 4, Episode 1 is unique in the fact that it was the first story to be done on the Secret Subreddit. It consisted of three major threats, a continually growing amorphous mass of flesh, a caustic red mist, and a zombie infection. A fourth major threat, in the form of surviving staff members deep within the facility's administrative section who had reverted to a tribal state in the darkness and renounced all forms of advanced technology other than what weapons and armor they could take from defunct Loki staging areas, existed, however it was shown much less than the other threats and was killed off en masse during the anti-matter core detonation, which it caused.
The blackout started at 1800 hours, when the small nuclear reactors, each powering a group of sectors, fell to an at the time unknown cause, which was later revealed to be the growth of the flesh throughout the vents and into the facility and into interference with the post-generation distribution of power.
Due to the Citadel falling and the nuclear meltdown, the facility was completely destroyed and the staff were stranded in a frozen tundra. The event ended with the facility destroyed but it was rebuilt in the aftermath.