Disclaimer:I mostly based this from what the conversation between Cama Zotz and Shade in Firewing. Since this is all purely fabricated by my own conclusions there is a huge chance that the text below is 100 wrong and there are some spoilers involved. All characters mentioned below belong to Kenneth Oppel.
I process no ill-will towards Cama Zotz even to this day. Is he not my twin brother? And after all we are supposed to be equals in this world. That is reason enough to respect him. We are different in our approach in ruling our kingdoms, yes but I'd thought he'd be satisfied with his role as I am with mine. I never knew that his subjects were yearning for their old life in the world I resided in but I knew that my brother was not happy and I almost thought he was jealous of me for some reason. We hardly ever spoke to each other, constantly busy with the realm we ruled over.
When we did contact each other, I often noticed how dejected he seemed. Back then I hardly knew anything of the Under world nor did I know of Cama Zotz's methods of treating his subjects. Even as I think of it, I almost find it funny how I never bothered to discover of what had become of my subjects when they passed away. I had always contented myself that my brother would care for them the same as I had done when they were alive. I trusted him. I almost pitied Cama Zotz for his sadness after a time and I decided to let him rule over any species of bat of his choice in the Upper World. I should have been more considerate of Zotz and find the source of his troubles but alas even gods can make mistakes. My brother had accepted my offer with grace and chose a rather strong and blood-thirsty species of bat to watch over. I thought that this would be the end of it but of course I was wrong. Eventually he requested if he could let the dead return to the world of living. I told my brother that it would be impossible for the living and the dead to coexist peacefully. He laughed at me and said that there would be no living. I was shocked at his response and asked of what he had meant. Zotz had scorned at the idea of life, saying there was no meaning behind it as all never escaped death and what a waste it was. He thought that there should be no life, only death so that all souls would be equal. He felt that without the constant necessities of life, there would be more peace. To him, this union of both our worlds was perfect. In an attempt to convince him that his idea was not just, I visited the Under world for the first time. I was surprised at it. All of it was just an imitation of the world I ruled over and the subjects were not content with it. Once again, Cama Zotz expressed his views and again I disagreed with him. He grew angry with me and asked how I could watch over my subjects drenched over in their own misery. He thought me heartless because I hardly ever intervened not like Cama Zotz. He constantly helped his living subjects, sending them dreams of the future and healing them. He laughed at the bats that to him seemed helpless and compared his subjects to mine. I still turned down his request. Still bitter, Cama Zotz tried to destroy me but only succeeded in separating my spirit from my body. As I felt the sorrow of those that were once my subjects, I decided to fulfill in some part of my brother's wishes. Using my power I transformed my body into a tree that would act as a portal back to the Upper world. They would not gain their physical bodies back but they could once again be part of the world that they had left. Using this tree, I returned to the Upper world where I still rule in much the same as before, barely intervening and simply watching. My brother is not evil, he doesn't understand my distance from my subjects. He merely believes that every event in the Upper world is because I plan it so. While many speculate over my existence and question my plans, I still love them. Because I love them, my only plan for them is simply live in the way that they wish to because I believe that this is the only way for them to ever truly be happy.