Black Mist

The Black Mist is the supernatural fog of undeath that pours from the Shadow Isles, a coal-dark shroud that kills the living on contact and binds their souls into spectral thralls. It was born from the greatest tragedy in Runeterra's history. When King Viego of Camavor, driven mad with grief over the death of his queen Isolde, invaded the Blessed Isles and plunged her body into the sacred Waters of Life to resurrect her, the magical catastrophe that followed inverted the islands' healing power into a force of pure death. The Ruination remade that paradise into the Shadow Isles and its people into undead horrors, and from that wound the Mist first spread. Left unchecked, the Black Mist is close to limitless. It rolls outward from its source, killing what it touches and dragging the newly dead back to swell the ranks of the Shadow Isles, and during the recurring cataclysm known as the Harrowing it surges across the sea to reach the shores of Runeterra itself. The thralls it raises keep the combat skills they had in life but feel neither pain nor fear, and the Mist can corrupt even powerful artifacts and beings. Yet it is not invincible. Strong light, and above all the holy light wielded by the Sentinels of Light, drives it back; it weakens the farther it strays from the Shadow Isles; and a will strong enough can resist its pull, for most of its thralls are mindless and only the greatest undead keep their own minds. Several powers bend the Mist to their purposes. Viego, the Ruined King whose sorrow first unleashed it, commands it still. Thresh harvests and torments the souls caught within it, Hecarim leads spectral cavalry charges through its ranks, and Karthus, who embraced undeath willingly, treats the Mist not as a curse but as a gift to be shared with the living.