Certain Doom

"Certain Doom approaches..."
This is a hardmode boss summoned by the Apocalyptic Sigil (will have a page soon) during any time of day. Its actual name is not Certain Doom, because I am currently uncertain about the name. I will change it when I come up with a name.

Fighting
After the full apocalypse has started (will be added with the sigil page), the screen starts getting dimmer, including the toolbar, life bar, mana bar, etc. Within 10 seconds, the entire screen is pitch-black, and it stays black for 5 more seconds. During these 15 seconds, the player cannot open their inventory, so they don't exit.

More will be added soon.