The Harrowing? What is it?

League's Halloween event. Spooky themed skins, and probably the Doom Bots game mode

doombots is super fun but it gets old after a while

riot's reason to make katarina skins

Its when the dead comes back to haunt you lol

According to Rito's lore, the Shadow Isles basically throw up all over the world and things glow blue.

This Harrowing event is a Non-Halloween theme with another reason to give Katarina her second Harrowing event skin. The skin theme this year is really just a recolor rip off from Soulstealer. Riot was extremely lazy this year. In the past, The Harrowing event used to be a Halloween Theme event that gave a spooky vibe. But that was last year. This year is nothing interesting.

The Harrowing is the day of the year where the black mist of the Shadow Isles tries to expand over Runeterra and consume as much souls as possible (Aka kill everything that has even a sense of life in it. So stuff like flowers also get consumed). Tough the mist's reach is stopped at Bilgewater.

Thresh and Hecarim (maybe Karthus too) leave the Isles for that day and search for souls / war.

What we see as a cool new map and skins is a brutal horror for the poeple in Bilgewater. Read the story Fortune and Shadow to truly understand what it is like to get attacked by the Mist (A long read).

The Mist expands further with every soul it consumes and one day it may be big enough to destroy all Runeterra.