That said, hooray for new inherent synergy!
I find it strange to consider a cost as "new inherent synergy". New and inherent I can see but usually costs are not called synergistic.
Often with deck ideas and card ideas (I think more the former than latter) I've seen many people say that so and so elements don't have synergy, or don't work together well. My view is that all elements have synergy - but the direct synergy that people often look for I call inherent synergy, because it directly ties the elements together.
I agree that direct synergy is synergy however there is more to synergy than 2 elements being used together. When the use of the second element is a bonus/benefit it is synergy. When the use of the second element is a cost to use the card then it is a cost rather than synergy.
So the inclusion of an off element activation cost is not synergy.
"Requiring Nightfall, Invisibility, Darkness Quanta and, Gravity Quanta are costs"
I would use Inherent Synergy to describe when a single card has 2 effects from different elements such that the 2 effects synergize with each other.
"Moving to different slots" and "Automatically attempting to devour opposing creatures" do synergize with each other. However I only see one element (Generic, Gravity) involved.
Direct Synergy I would describe as when an effect on a card has synergy with a card of a different element than the effect on the first card.
"Devour" and "Nightfall (extra hp)"
However a good example of direct synergy would be a card with 2 effects from different elements such that each effect had cards from the opposite element that it synergized with.