@Ribath In this world/verse, Gods are living sentient concepts. They emerge when the concepts they represent emerged. It's unknown if the concepts/spheres they represent would cease to be if they disappeared, but they do embody those concepts.
So yeah, they are Gods in the monotheistic sense, but that's a given considering that there are many of them. It's better to view this from a polytheistic point of view. In such myths, the first being to exist isn't omnipotent. It's just the first being, and it contributes to the creation, and with its part of creation other beings(gods) also come to be without being directly created by the first being, and they too have a role in furthering creation. This is how it is in Greek, Norse and Egyptian mythologies, same for many others (including Hinduism, Shintoism and many others).
Then there's Zoroastrianism, which is closer to the monotheistic point of view, though this one only has two true Gods, with the first being closer to how a monotheistic God is. Zoroastrianism very likely inspired some of the core aspects of Judaism, and by extension most monotheistic religions, but that's beside the point in the case of this story.
So back to the gods in this story being sentient concepts, maybe thinking of Thanatos from Greek myths is a good comparison. In Greek mythology, while the Gods and Titans are associated with concepts, most of them are actually just experts in the fields associated with them or just have influence over the domains associated with them. Thanatos is one of the exceptions due to people no longer being able to die if Thanatos is chained down.
In this story, the gods didn't come to be from relations with each other, nor did they come to represent a concept after their birth. The Gods here came to be alongside the concepts they represent.
Stagnation was originally among he "good"-aligned Gods, but technically speaking his sphere is more neutral. it's just that personality-wise he was more good-aligned than not (and still is). Then, over time he broke precisely because he cared too much.
I personally really like how Gods are depicted in this verse. Them changing isn't about them being Gods or not, but rather about them being sentient, though with a twist. The twist being that while they are sentient, they are also bound to a concept that define them to their core. That concept thus influences their psychology in different ways depending on how it aligns or contrasts their developed mind from their sentience.
Stagnation represent the absence of change, but due to balance of the world between its many concepts, it contrast with the flow of the world. He personally grew to love the living, and that's how his sphere adapted itself to the many concepts in the world, by focusing on the good times and not wanting them to end, accommodating his desire for things to not change with wanting the ones he grew to care for to not die. The change in question being death. The absence of change being the preservation of life as much as possible. He loves the living and those who achieve great things, but despairs when they fall. And so, due to this stance, he was more so good-aligned than neutral or evil. Problem is, his sphere contrasts with the way things are. People die, whether from violence or natural causes. With how much time has passed since the beginning of the world, it makes sense for him to have broken. The nature of his sphere is more neutral, but could no longer stand not to act, and after breaking down, Undeath became his solution.
Thinking back on how the Undeads in the destroyed village were, it showcases how Stagnation views this. The little girl and the others weren't mindless. At first, in the first arc, it seemed as though most Undead were mindless, but those Undead that Will fought were of demons and such. Stagnation doesn't seem to care much for them, especially with those being actively pursuing to end most living beings. That's one of the reasons why Stagnation made the deal with Mary, Blood and Gus. He didn't want the demons to win, and he didn't want the 3 heroes he admired to die. It's likely that the Undead demons in the fortress were turned into Undead with the intent of serving as mindless guards to the seal from people and demons from outside.
Then there's also how the "heroes" Stagnation summoned to fight Will were mostly mindless. It's likely that the human mind isn't powerful enough in most cases to remains conscious in Undeath for eternity. Stagnation seemed to believe that Blood, Mary and Gus would be able to remain themselves for eternity even in Undeath, and he seemed to believe the same for Will. So maybe the little girl and the others from the destroyed village would've lost their minds with time too. And this to me proves even more so that Undeath isn't a good solution. It ends up with Stagnation only suffering more when the Undead lost their minds, and then there's also how when the living reject the Undead (such as with what the elf almost did with the little girl), it breaks down that Undead's mind even more.
So yeah, I really like Stagnation and the depth of his character. He's not evil per se, but he's lost himself in his desperation.
I apologize for this long comment (and my tangents within it), but to conclude, this is how the Gods are in this verse and it has already been explained (the core concept of it) in the early chapters of even the manga adaptation. When one concept/God came to be, its opposite also came to be, and on and on.
