The last level in the Pleiades system, Brazen Vortex, is heavily infested from the beginning. You must find several triggers to access the red key. Inside the Red Area is the boss, which you aren't informed of in the briefing.
The fort has a complex structure and also contains a few secret areas, however small they may be. Some are particularly useful.
You must find 5 triggers and destroy them to obtain the red key. You will then proceed to destroy the boss robot, which is armed with Fusion and Mercury Missiles.
There are two cloaks and one invulnerability near the boss, but these are hidden.
Class 3 Heavy Driller