Consciousness is a relationship identification tool. Every concept requires a relationship be established (Perception works the same way). For that relationship to be valuable to you, it has to be relevant to your goals and purpose. You therefore need two things: 1) A factual relationship 2) A relevant relationship (to your goals and purpose at hand) Epistemology is the bridge that connects Metaphysics to Ethics and Vice Versa (tool for survival)
If you were Aristotle you'd say that you could have an essence of a single existent (by itself) - Metaphysical. But for Rand essence are things viewed in a certain relationship, essence is Epistemological not Metaphysical.