"Twin souls" are the heart of Atvatabar culture. These are young people are brought up to worship self denial.
We watch thousands of "twin souls" parade past, being showered with jewels. These couples love each other intensely, but will never have children.
They believe that their self restraint produces the power that runs the civilisation. As if to prove it, we are next taken to the "sacred island of Arjeels". A sorcerer with an electric cable tells me that they must have a certain number of Twin Souls, or else this sacred island will sink into the sea.
Later we see a resurrection ceremony, where they believe that Twin Soul Energy (and electric sparks) can sometimes bring a dead person back to life.
I think the symbolism is interesting. My outer world is in the Victorian age. This inner world is like the Victorian inner subconscious: The desire for a highly ordered society driven by control and denial of passion. Yet they worship a goddess who often wears very few clothes. I think the real energy is the tension between what they say they want, and what they really want.