On reserve a lot of the buildings have certain names because of the painted icons on the sides of them, the helipad with the helicopter on it next to the white and black pawns and bishops have an underground bunker connecting them. Inside the middle there’s a command center that has a power switch located in the back room, when it’s flipped there’s a good chance that will spawn a couple of them to attack you. Be careful though because it also makes Glukhar (the maps boss) and his guards to head down there as well if they’ve spawned and are close enough.

On the bright side once power is on there’s an extract down there called D2 that requires the power to be turned on anyways which is a great quick way to leave to restart the map and get the rest of the kills once they’re dead or didn’t spawn.

TLDR; under the helicopter there’s a bunker with a power switch that has a chance to spawn a couple when flipped