Light and Dark etymology
Now, I know what all of you are probably asking right now.
While the Dungeon may be portrayed as in the darkness underground, and the Gods within the light of the surface, we know that the Winnower and Gardener encompass concepts far more complex and meaningful than the average light level of ones residence.
Did the lore not say it too us? Did the Speaker not give us an example? The Light is the willing sacrifice, given freely for a noble goal.
The protein that kills cancerous cells to protect the rest of the whole is not of the Dark, but the Light.
That is what the Travellers philosophy means. Why it favours humans as Guardians instead of the Fallen scavengers.
Which faction portrays that more closely?
Adventurers are no difference than the Risen the Iron Lords rose from. Selfish and ruthless, killing each other for their own goals, whether it be their god, or something as simple as money and wine.
On the other hand, monsters work hand in hand to reach the surface, all sacrificing themselves for their 'Mother Dungeon'. We even see hordes of monsters sacrifice their own lives for Demi-spirits to further this goal.
Yet it is not so simple as thus.
While Adventurers granted the Falna are no different from the Risen before the founding of the Last City, as a whole, if you consider those of them that truly matter and that their Falna is created with the Arcanum of each of their Familia's Gods, that all of them do co-operate under the Guild to keep the Dungeon sealed.
Then that the Demi-spirit is somewhat separate from the dungeon and the monsters sacrificing themselves like do not do so out of choice. That they wish to wreak havoc among the surface dwellers, that Monsters do kill each other for Magic Stones, that Xenos are both kind and intelligent and we start to see that things to do not fall into the light and dark pattern.
So why do I still insist that the Dungeon Monsters smell of the Darkness of the Winnower, while Adventurers glow a light akin to that of the Gardener yet wreathed in their Gods and Goddesses Domain?
Simple. The Winnower and Gardener are older than the Universe itself, they have created countless Universes in their contest, and are concepts of reality, something so basic and central itself, that to replace it you would need something similar.
No, there is nothing quite like the Light or Darkness in Gekai or even Tenkai. But the Gods and the Dungeon certainly rival them.
If for no other reason than the Dungeons imprisonment mirroring that of the Worm gods imprisonment on Oryx's former home, I feel that conceptually they would feel the same to any Guardian not a Warlock truly versed in the intricacies of the Light and Darkness.
As for whether the Dungeons Magic will affect our protagonist as the Dungeon did, I can say that the similarities are too many to ignore. Monsters weapons are reforged by children touched by the gods into something greater than the sum of their parts after all. Not too different from Crota's shattered blade being reforged into a weapon befitting a Guardian.
That said, the Dungeons aura will only hinder our Guardian from reviving himself in the Deep floors, and even then only when he exhausts much of his Light. Since what Ghosts do is such a delicate manoeuvre I can see this as plausible, though any adventurer at level 2 or higher could easily assist, and it would do no more than slow Sirius down, as only something with the firepower to destroy mountains or the conceptual advantage of a gods Arcanum or a spirits magic could harm Sirius through his defences. Though such things aren't uncommon in the Dungeon.