Peace's answer to this was very good. I'd just introduce a different phrasing here to express the same idea, but in a way that tends to "hit the right key" for me.

The basic and most primordial aspect of you, the subject, is transcendent. Nothing, but by being outside of a system, can have knowledge of that system. Difference is key. A flake in the Frosted Flakes box cannot know about other flakes. If it were alive it may react instinctually and, more or less, by way of purely psychological kinds of learned responses. But it could not know.

The intellective act is therefore carried out by a subject which transcends the system. We say the subject is transcendent with respect to the system.

Now, contrast this term with transcendental. The faculties themselves by which you do the intellective act of reasoning here within the system are transcendental. Think of the transcendent as an upward pointing triangle, and transcendental as down.

The union of these represents the subject experience you have here. Your intellect transcends this system, forming the grounds for you to know and pointing upward at the source. Descending and issuing from the mind are the faculties that do the knowing, the transcendentals, a priori things like cause and effect, space and time.

The thing I believe you sense is what Kant called the "thing in itself". You sense that you are seeing the apparent, but not the real. There is a world behind the world.

That is absolutely the case. We have been using causality in a purely horizontal sense here - temporal causality. I suspect that the "relationship with this Essence" of which you speak, as something "beyond Causality", is actually what I and others would term "vertical causality" - a non-temporal causal connection between you and this essence. Our intellect - our knowing faculty - has a vertical nature, whereas our reason is horizontal insofar as it is discursive, from A to B to C.