I interpreted it as Polaris as a resonance entity, in the same way the Hiss are, and Hedron as a more physical or observable entity that was able to tap into the Polaris frequency of some form. Polaris' frequency counterbalances the Hiss resonance, rendering them neutral and preventing dissonance, and was thus able to project itself primarily through Hedron (hence the protective measures). Polaris is seemingly able to resonate through other entities (because they're special, or because they're chosen), which it has done before, and so once Hedron was destroyed Polaris began using Jessie specifically as a conduit.
But the game is full of ambiguities of entities, their affiliations, and their motivations.
There's the Board, which communicates through the black pyramid, and is directly tied to The Old House and the black pyramid door at the lodge.
There's the Former, which the Board seems familiar with, existing in its own astral plane as a physical entity and corrupting altered world objects in our reality.
There's the Hiss, which appear to be resonant based and have no physical form, and come from one of the dimensions accessed through the projector slides.
There's Polaris, another resonant based entity, also accessed through the projector slide dimensions.
There's Hedron, a physically based entity and conduit for Polaris resonance, that is found in the same slide that Polaris was found.
There's the Not-Mother, an unspecified physical entity that fed the boys 'milk' and turned them into monsters, from one of the projector slide dimensions.
There's eisseJ, a physical copy of the reality distorted by the mirror, an entity of some sort within able to take on forms of its reflected surrounds.
And there's the general ambiguity surrounding objects of power, altered world objects, and what source gives them motivation and intent.
Then, of course, Ahti.
It's good shit.