The "day and night" in True Hell are entirely different from the Human World; there is no sun or moon here, and the world's hues relate solely to the pervasive ash smoke in the sky.
The birth of the powerful,
Wars and deaths,
The spread of plagues,
Activities of the world itself,
And the release of certain powerful spells all lead to copious ash rising,
The ash generated around the world gradually obscures the sky, causing True Hell to grow dimmer until it is engulfed in pitch blackness.
When the darkness reaches a certain level,
A special world mechanism activates.
The "Special Force - Hunger" then faces the sky together, devouring the ashes. Visible dark ashes are swept across to the other end of the world, and light reappears.
This cycle of ashes thus forms the day and night of Hell; coincidentally, the cycle happens to be 24 hours, which is also considered as [one day] in True Hell.
