Why the Black Mist hasn't overtaken Runeterra yet
The Black Mist goes forth every harrowing, getting stronger and stronger every year. Why has it not gone farther than it has? My solution to this question is some assumptions on the properties of the Mist.
- The Mist acts like Zerg Creep in Starcraft, granting power to the specters in it. Powers like levitation to cross the sea, immunity to physical attacks via becoming incorporeal (as seen in several bios) and collecting the souls of any people who die in it. So if the mist grants these powers, how has it not overrun the continent?
- The mist has a set "lowest density" before dissipating. This prevents the mist from spreading too thin, and forces it to try, every year, to attack the nearest human settlement for souls: Bilgewater.
- The maximum amount of mist is determined by the number of enslaved souls. This the more Bilgewater residents die, the stronger the mist becomes.
- The cache of evil relics is the "nucleus" of the mist, so the mist cannot just move like a cloud of locusts.
These points explain the characteristics of the black mists and why Valoran is inhabited by more than ghosts. I also have a theory on why Demacian steel is said to be effective against the various ghouls, but that is for another thread.
