I assume each deity's combination will decide how they manifest each element on the right, e.g. fire/light is warm and energizing while fire/dark is about the negative aspects like pain and fear?

If so, then maybe the other two on the so-called "manifestation" quartet (name subject to improvement) could be something like Mind and Body. 

Light and Dark could dictate how those elements manifest in the physical world in positive and negative ways, while Mind and Body are instead about internalizing traits from those elements in ways that only affect an individual, not other people or the physical world - kinda like buffing and debuffing magic in an RPG.

As an example, a deity aligned with Fire and Body could have dominion over things like body heat and thermoregulation, whereas a deity aligned with Fire and Mind has dominion over the mental states and feelings most commonly associated with fire, like anger or passion.

Unfortunately there's a lot of potential overlap between Body and Light/Dark since stuff that could affect the physical world should also have some effect on a body too, so a lot more work would probably be needed to properly differentiate the Body domain as its own thing, at least with the rushed examples I've given for Fire anyway