system
Given the following post, respond as if you're commenting on Reddit:
human
[Dark Souls 3] Ok, what is actually going on with the sun?

From down here it looks like a black hole and is literally bleeding sun material down to the Earth. I understand the flame is dying so thats it but surely it would just become dimmer and dimmer without doing all that freaky stuff?
gpt
In the first age of fire, Gwyn created a number of seals aimed at preventing the age of dark from ever coming to pass.  The bonfires, the darksign on humans that causes them to become undead, the time stasis through fillianore, and lastly himself linking the first flame.  By the time of DS3, the age of dark is pressing so hard against those seals that it is leaking through, turning the sun black and causing oozing darkness to seep through into the world.

In past cycles like DS1 and DS2, the age of fire was slowly fading, but it hadn't gotten this bad yet.  Few people truly understood the cycle, so it was just a matter of time before some undead champion successfully linked it.  In DS3, prince Lothric has been actively preventing the first flame from being linked.  He *wants* the age of fire to end, so this ending of the cycle has gone on much longer than any previous one.  The Ashen one is a truly last ditch effort from Gwyn's long-dead magic attempting to "fix" things.