Since essence deals with conceptual properties, of a conceptual model, existence values can be associated with particular concepts. If an existence value is high, the concept is true and objective and real. In this sense, essence goes with ontology. To shift from matter to a great thought is still conceptualizing. Both can have high existence values.
Ontology emerges from epistemology when organisms evolve sufficiently to conceptualize.
Ontology is cultural. I use 'ontic' as a short form of 'ontological'. The dictionary notes that 'ontic' refers to the real rather than the phenomenal, while it defines 'ontology' as the study of levels of existence. I see these terms as, at least, related, if not interchangeable. Again, I have no idea what is meant here.