Hi! You seem to think that having "intrusive thoughts about mutilation, bodily catastrophe, death, and of non-existence after dying" has some kind of deeper meaning. You seem to want to explore what these thoughts say about you as a person. Perhaps you wonder "Why these thoughts?" as opposed to other thoughts? These are the kinds of thoughts that an untreated depressed brain creates. Once your depression is adequately treated, the thoughts will go away. There is no deeper meaning than that. I would focus all my attention on treating the depression.