Games like Spectral Prison
Games like Spectral Prison include MiSide, Mouthwashing, Firewatch, Layers of Fear (2016), and What Remains of Edith Finch. We matched them by the tags players give Spectral Prison on Steam (Walking Simulator, 3D, First-Person, Horror, and Psychological Horror): closest matches first, and among equally close ones the better-known games.

MiSide
Shared: Psychological Horror · Horror · First-Person

Mouthwashing
Shared: Horror · Psychological Horror · Story Rich

Firewatch
Shared: Walking Simulator · First-Person · Story Rich

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

What Remains of Edith Finch
Shared: Walking Simulator · First-Person · Story Rich

Phasmophobia
Shared: Horror · Psychological Horror · First-Person

SOMA
Shared: Horror · Psychological Horror · Story Rich

Amnesia: A Machine For Pigs
Shared: Walking Simulator · Horror · First-Person

Summer of '58
Shared: Horror · Walking Simulator · Psychological Horror

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

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

Outlast
Shared: First-Person · Horror · Psychological Horror

Garten of Banban
Shared: Horror · First-Person · Psychological Horror

The Beginner's Guide
Shared: Walking Simulator · First-Person · Story Rich

The Park®
Shared: Walking Simulator · Horror · First-Person

Fears to Fathom - Ironbark Lookout
Shared: Horror · Psychological Horror · First-Person

Blair Witch
Shared: Horror · First-Person · Psychological Horror

From The Darkness
Shared: Horror · Psychological Horror · First-Person

Welcome to Kowloon
Shared: Horror · Walking Simulator · Psychological Horror

Scanner Sombre
Shared: Walking Simulator · Horror · First-Person

KARMA: The Dark World
Shared: Walking Simulator · First-Person · Horror

Poppy Playtime
Shared: Horror · First-Person · Psychological Horror

Buckshot Roulette
Shared: Horror · First-Person · 3D

9 Childs Street
Shared: Horror · Walking Simulator · First-Person