I hope I've narrowed down the general idea of my question enough-- Basically, I've started with the idea of a desert society with access to a hidden energy source ruled by a body of immortals. At least, I'm playing with the idea of them having access to longevity, with the city's founders ruling the city still.
This is a post-apocolyptic world, where the rest of humanity is (supposedly) wiped out. I want my rulers to divine ways to keep the city's occupants from leaving the city without using mind control.
The problem is, I'm having a lot of difficulty thinking of reasons a governing body might endeavor to this level of deception to the public.
Honestly, I'm just looking to toss get some outside perspectives on these concepts-- I've been considering this for so long, I'm having difficulty thinking outside the box and need to discuss it with others.