Games like 18Hell:Lost
Games like 18Hell:Lost include What Remains of Edith Finch, Firewatch, Layers of Fear (2016), Amnesia: A Machine For Pigs, and Firework. We matched them by the tags players give 18Hell:Lost on Steam (Walking Simulator, Psychological Horror, Atmospheric, Horror, and Old School): closest matches first, and among equally close ones the better-known games.

What Remains of Edith Finch
Shared: Walking Simulator · Atmospheric · Mystery

Firewatch
Shared: Atmospheric · Walking Simulator · Mystery

Layers of Fear (2016)
Shared: Psychological Horror · Walking Simulator · Horror

Amnesia: A Machine For Pigs
Shared: Walking Simulator · Horror · Atmospheric

Firework
Shared: Horror · Psychological Horror · Atmospheric

SOMA
Shared: Psychological Horror · Horror · Atmospheric

Little Nightmares
Shared: Atmospheric · Horror · Singleplayer

Mouthwashing
Shared: Psychological Horror · Horror · Atmospheric

MiSide
Shared: Psychological Horror · Horror · Atmospheric

Poppy Playtime
Shared: Horror · Psychological Horror · Singleplayer

Little Nightmares II
Shared: Horror · Atmospheric · Psychological Horror

Sally Face - Episode One
Shared: Psychological Horror · Horror · Story Rich

Outer Wilds
Shared: Mystery · Atmospheric · Story Rich

Garten of Banban
Shared: Horror · Psychological Horror · Singleplayer

Outlast
Shared: Horror · Atmospheric · Psychological Horror

Still Wakes the Deep
Shared: Psychological Horror · Horror · Walking Simulator

The Vanishing of Ethan Carter
Shared: Atmospheric · Walking Simulator · Mystery

No, I'm not a Human
Shared: Psychological Horror · Horror · Atmospheric

INFRA
Shared: Atmospheric · Walking Simulator · Mystery

The Park®
Shared: Psychological Horror · Walking Simulator · Horror

Call of Cthulhu®
Shared: Psychological Horror · Horror · Atmospheric

Resident Evil 7 Biohazard
Shared: Horror · Atmospheric · Psychological Horror

KARMA: The Dark World
Shared: Walking Simulator · Psychological Horror · Horror

In Sound Mind
Shared: Psychological Horror · Horror · Atmospheric