If you stand near Zavala and look out into the City, You'll see several buildings lights flicker on and off or even shut off entirely. You stand near Banshee's stall, you'll see and hear the lights die. You go through the Annex and the hallway lights flicker on and off or even shut off entirely for a few seconds to even a full minute (depends on which platform you use) Either the Last Citys power grid is failing due to it being Eternal Night, The future War cult causing the blackouts and will eventually blame the Eliksni for the power fluctuations giving the people a reason to continue attacking them, or its the Vex doing psychological warfare on us.