Stories that I found to be suspenseful or to contain elements of horror:

Til the End of the World

Author: resonae
Pairing: Tao/Kris, OT12
Rating: M
Length: 3131 wc
Summary: Zitao's world doesn't end even when the undead overrun the earth.
Warning for character death(s). the walking dead type fic. a tao-centric angst-fest with zombies and two goodbyes. characters referred to by given names.

Dream House

Author: lunathunderhead
Pairing: Sehun-centric, Kris/Chanyeol, Chen/Suho, Luhan/Kai
Rating: R
Length: 3900 wc
Summary: Come out, come out, whatever you are...
>:/ scared me before heading off to bed. urbanlegends!exo for you to feast your eyes on. lunathunderhead does such nice horror.
 

Darkest Hour

Author: junxouji
Pairing: Sehun/Kai
Rating: M
Length: Ongoing 
Summary: FBI agent Sehun is tasked to help investigate the disappearances of young girls across Seoul to Beijing - who are left with their bodies mangled in horrible ways. The investigation weighing heavily on Sehun's state of mind and sanity, who is not use to the horror outs