Webtoons is a website dedicated to online comicbooks where a large portion is contributed by Koren horror comicbook artists. The latest series called Shriek, which means 'scream' is a masterpiece of artwork, combining artistic visuals with sound effects.
Without getting into details let me just mention that episode 1, called 'A Ghostly Job' begins its dark story in a mental hospital where ghost sightings are reported occasionally. Whether these are just a product of pateients' distorted imagination or there is something going on, it's up to you to judge.
The third episode is also very cool, and dark, and it's called "Scratching" by Jingook Lim... Little less dialogs, but very good visuals with sound effects which completely draw you into the story.