Kill6BillionDemons II: The Successor's coming will be followed by 108 burning threads

[Onyavar]

I think the sins still fit pretty well, if one takes a broader definition of them than the modern pop culture one. Luxuria, the original lust, is not necessarily sexual. It any desire for anything that is too strong. Money and power are explicitely named in older sources and of course the author of this webcomic would go look at those older sources. Incubus explicitely seeks out the Lustful and gives them their wishes.

Gluttony, similarly, isn't necessarily food. It's overconsumption in general. Taking more than you need, so that nothing is left over for others.

Pride is interesting. Superbia is in one definition more like hubris, thinking that one knows better than god or the gods. BUt a part of it is also not seeing the accomplishments of others, only one's own. And of course, overstimating one's own accomplishments and forgetting one's flaws.

I don't know, they all fit pretty well.

True, they fit. I played a bit with the topic and put them down as follows. In case of the bolded ones I found the arguments very compelling.

Incubus: Envy (He just isn't lustful. But if you pay attention, he is deviously seeking to ruin others, deprive them of their possessions and drag them into the mud. He may not want things for himself, he just can't abide that others have something good. That is the definition of malicious envy.
Mottom: Sloth (in the form of cowardice and apathy. She was living in fear of her own courtiers, and all her acts so far have been a reaction to the acts of others)
Gog Agog: Lust? (No backstory yet, they are the demiurge we know the least about. But still they have been described as being really large in the "entertainment business" on Throne, and we have seen them surrounded by beauty attendants)
Solomon: Wrath? (We just learned what his original motivation has been: seeking revenge. We have seen him obliterating his head monk's head in a fit of rage. Sure, he seems like the cool guy, but I'd say he has a temper. In the rare cases he flips out, people die.)
Jagganoth: Gluttony? (No backstory yet, so this is speculation. But we have seen him in the shape of an overweight brute... and gluttony is also related to selfishness, which might fit the character although we know so little about him. Could be that he realized that he needed to work out in order to grow and devour even more.)
Iadis: Pride. (In an act of Hubris, she gazed at the true shape of the universe which made her insane)
Mammon: Greed. (very straightforward: it just fits him best. Until we know more, that is.)

Spoiler: Also, some unrelated backstory speculation:

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Incubus is seen as the placeholder of Maya, and it rankles with him. But we already know that there were many more demiurges. We learned how Solomon dealt with two others. So, what about the rest of the competition? I have just thought, that it could well be that Incubus was already a demiurge under Zoss (this recap flashback backs it up, although it looks like a symbol picture only showing the surviving demiurges). What if Incubus has been playing the grey eminence before, pretending to be just a minor competition? What if the other demiurges have seen him just as Maya's lackey... when in reality, he was the driving force behind Maya's ambition to build up the middle army? Until, at one point, they had a falling out: Either he pushed Maya too far, or she finally saw through his schemes. However, she as his figurehead, brought up the willpower to abandon him; and because she was such a powerful player in the demiurge business, the others never accepted that Incubus who was officially just her "right hand man", finally took the throne that was "hers". I think this speculation fits the story we have been told so far.