Alien Redenzvous is the fifth level of the episode 'Plug 'N' Pray' in Duke Nukem: Total Meltdown.
The secret level 'Faces of Death' can be accessed by pushing all the switches below the large pillar which has a Battlelord Sentry on top. Once pressed, the wall on the far left to where you originally came in will open and reveal a passageway which leads to the exit.
If played on the hardest difficulty setting, 'Come Get Some', there will be eight battlelord sentries on this level, four of which can be found in the same area! Good luck!