Maybe I am trying too much to read between the lines here but...what is it about G'raha's soul and the Allagan eyes?

In 5.3, we see Elidibus trying to do something to G'raha and say
"Though you lack her blessing, your soul is surprisingly dense"

For a long time I thought "well yeah, he lived through one more rejoining than everybody else".
But I struggle to understand the relevance of that line at that moment in the story, as it sounds so much like a foreshadowing of some sort...

So it led me to questions about the Allagan bloodline as a whole.
What is it? What is that red eye?
Since Emet was involved in the Allagan empire, was that eye a new trick of his?
When G'raha got his second red eye, what did it mean? There was this line from Doga at that moment : "Know that as long as this light of hope survives in you, our souls will still remain- even if our bodies are lost"
So, did Doga/Unei souls rejoin with G'raha?
Unei also said 'We will share our blood with you. Though it's effect will be but ephemeral, it will bolster the Allagan presence within you."
Is G'raha going to lose his red eye at some point then?...Are Unei and Doga souls going to leave him and go to another body later? Similar to Ascians souls then?

Can the eye be somehow related to Garlemald, and Fandaniel saying "could Emet Selkh have found a way?"? Is it a coincidence that the Resonant have red eyes too?

So I guess my question is...do we have any information on the red eyes function and what they are exactly? Or is it just as vague as many other plot elements introduced early on to leave some room for future plot?