Guardian (Final Fantasy VI)

The Guardian is a machine in Final Fantasy VI created to defend the Imperial Palace in Vector. It is indestructible, and the only way to get around it is to run away. Of course, that does not allow anyone to pass the Guardian. Players first encounter this enemy if they try to access the Imperial Palace on their first visit to Vector. They can encounter it again if they try to enter Vector after destroying the Magitek Research Facility and if they try to leave Thamasa or talk to the Magitek soldier behind Kefka while controlling General Leo Cristophe. In Kefka's Tower, the Guardian reappears, but this time it is now vulnerable.

Kefka's Tower version
The Guardian at Kefka's Tower can be a difficult boss. It runs several "Battle Programs" which can deal massive damage. Each Program mimics a former boss from the World of Balance. Between each program, it resets to its weak default mode. Its Programs run in this order: Ultros, Dadaluma, Air Force, Ultima Weapon. In particular, Dadaluma's program can be dangerous because it Throws weapons at the party for unblockable damage ignoring defense. Ultima Weapon's program is also dangerous because it uses Flare Star and Mind Blast. Thankfully, Guardian is weak to Lightning, which is an easy weakness to exploit with Thundaga. Also, if Locke is in the party, he can steal a valuable Force Armor, which is an armor that comes in limited quantities.