My family lived in Yuma Arizona when they filmed that scene from Return of the Jedi in the sand dunes nearby. I wanted to try to go see the filming, but my mother wouldn't let me 
The Shadow Tower isn't alive or anything like sarlacc - basically, there was an ancient powerful kingdom whose king held a mighty weapon. In truth, the king's power came from the 'Darkness' and he held secret rituals for the Darkness- presumably tossing people into an otherworldly dimension of some sort where they wander lost and tormented forever. His weapon (the one with the eye) gives him power to control the Darkness. When his kingdom is finally defeated and falls apart, he retreats to his Tower built in the 'Darkness' but eventually, the Darkness turns on him because he isn't sacrificing victims anymore. As the latest victim sacrificed to the Darkness, the player is sent to defeat the king and take his weapon . . then the zaniness ensues!
The Shadow Tower isn't alive or anything like sarlacc - basically, there was an ancient powerful kingdom whose king held a mighty weapon. In truth, the king's power came from the 'Darkness' and he held secret rituals for the Darkness- presumably tossing people into an otherworldly dimension of some sort where they wander lost and tormented forever. His weapon (the one with the eye) gives him power to control the Darkness. When his kingdom is finally defeated and falls apart, he retreats to his Tower built in the 'Darkness' but eventually, the Darkness turns on him because he isn't sacrificing victims anymore. As the latest victim sacrificed to the Darkness, the player is sent to defeat the king and take his weapon . . then the zaniness ensues!