An important passage by Nagarjuna explaining that all manifestation are in essence Dharmadhatu or Buddha-Nature. It explains Dharmadhatu and Consciousness as the very manifestation that dependently originates and is empty.
Arya Nagarjuna:
38. When eye and form assume their right relation,
Appearances appear without a blur.
Since these neither arise nor cease,
They are the dharmadhatu, though they are imagined to be otherwise.
39. When sound and ear assume their right relation,
A consciousness free of thought occurs.
These three are in essence the dharmadhatu, free of other characteristics,
But they become "hearing" when thought of conceptually.
40. Dependent upon the nose and an odor, one smells.
And as with the example of form there is neither arising nor cessation,
But in dependence upon the nose-consciousness’s experience,
The dharmadhatu is thought to be smell.
41. The tongue’s nature is emptiness.
The sphere of taste is voidness as well.
These are in essence the dharmadhatu
And are not the causes of the taste consciousness.
42. The pure body’s essence,
The characteristics of the object touched,
The tactile consciousness free of conditions—
These are called the dharmadhatu.
43. The phenomena that appear to the mental consciousness, the chief of them all,
Are conceptualized and then superimposed.
When this activity is abandoned, phenomena’s lack of self-essence is known.
Knowing this, meditate on the dharmadhatu.
44. And so is all that is seen or heard or smelled,
Tasted, touched, and imagined,
When yogis [and yoginis]* understand these in this manner,
All their wonderful qualities are brought to consummation.
45. Perception’s doors in eyes and ears and nose,
In tongue and body and the mental gate—
All these six are utterly pure.
These consciousnesses’ purity itself is suchness’ defining characteristic.