The keywords are :
metaphysical
visionary
theology
spiritual
From Google:
Metaphysics is a major branch of philosophy. It concerns existence and the nature of things that exist. ... The metaphysical idea that reality exists independently of one's mind and yet can be known is called realism. The metaphysical idea that no mind-independent reality exists or can be known is idealism.
So any book which has a spiritual component, visionary in nature, based in theology, or deals with the nature of existence in some sort of way, can go in the sub-category.
Most of my books have some sort of spiritual component, or use of higher beings based on deities used by various religions and belief systems.
I also bend the nature of things, these days by a combination of supernatural and magical means.
I also interpret it to be an exploration of self, and since I write first person life in space, there is always an exploration of the existence of the MC and how they fit into reality.
Metaphysical & Visionary is usually my best sub-category.