Defeat the Fallen to invalidate the Vex experiment.
- Go up the "stairs" that appear in front of you. This will bring you to a large platform.
- On this large platform you will find a number of Wretches and Dregs. Defeat them.
- Clearing this platform will cause a second to appear with a number of floating platforms leading toward it.
- These floating platforms are phasing in and out of the timeline you are in. Move across them carefully.
- This second platform has a number of Vandals, Wretches, and a Fallen Rear Guard.
- Clearing this platform will cause another to appear.
- Once again, you will need to use the phasing platform to reach the third platform.
- This will lead you to a cliff edge with a number of Shanks, Dregs, and Servitor.
- Clearing this area will lead you to the Fallen Captain.