This page of our Control guide contains a walkthrough for a side mission called A Merry Chase.
To start the mission, take the elevator down and travel to Janitor's Office, not far from the entrance to NSC Power Plant
Walkthrough: Go to the Janitor's Office and you will see red, flickering lights. Go into the room with them and the floor of the room will crumble. You've entered the astral plane - follow the horse, who is another Item of Power.
You'll unlock a completely new power - evade, which is a dodge applied in a chosen direction. Using it, you'll be able to get out of this level, quickly avoiding e.g. crushing walls.
Using this ability, you can perform dodges in air, easily avoiding enemy attacks. This is a key ability that is incredibly useful further ahead. The quest ends with a reward: crafting materials, modifications, and up to 2 skill points.