Oh crap, what I'm getting myself into...
Super Tyrian is a secret gameplay mode from Tyrian. In order to access it, you have to type ENGAGE on the title screen. If done correctly, the announcer will say "Danger" and the screen will blur and fade out.
Super Tyrian follows the same rules as the Arcade Mode, but with a few twists. The difficulty is automatically set to Lord of the Game (the hardest in the game), though it is possible to lower it to Suicide by holding the Scroll Lock key while the screen is fading. While your ship is set to The Stalker 21.126, all cheat codes are disabled and your line of sight is reduced to only 90° in front of your ship, much like in the Assassin mission but for the entire game. You're also limited to only the Atomic Railgun front weapon and cannot upgrade or obtain weapons other than Special Weapons.