Games like The Immemorial Order
Games like The Immemorial Order include Firewatch, What Remains of Edith Finch, Sally Face - Episode One, Mouthwashing, and Alan Wake. We matched them by the tags players give The Immemorial Order on Steam (Horror, Psychological Horror, Mystery, Jump Scare, and Adventure): closest matches first, and among equally close ones the better-known games.

Firewatch
Shared: Adventure · Mystery · Walking Simulator

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

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

Mouthwashing
Shared: Horror · Psychological Horror · Atmospheric

Alan Wake
Shared: Horror · Adventure · Psychological Horror

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

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

SOMA
Shared: Horror · Psychological Horror · Atmospheric

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

[Chillas Art] The Convenience Store
Shared: Horror · Psychological Horror · Adventure

MiSide
Shared: Psychological Horror · Horror · Story Rich

Little Nightmares II
Shared: Horror · Adventure · Psychological Horror

Phasmophobia
Shared: Horror · Psychological Horror · Mystery

Firework
Shared: Horror · Mystery · Psychological Horror

Outer Wilds
Shared: Mystery · Adventure · Story Rich

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

Oxenfree
Shared: Mystery · Horror · Story Rich

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

DON'T SCREAM
Shared: Horror · Psychological Horror · Jump Scare

Fears to Fathom - Ironbark Lookout
Shared: Horror · Psychological Horror · Atmospheric

DREDGE
Shared: Adventure · Mystery · Psychological Horror

Poppy Playtime
Shared: Horror · Psychological Horror · Mystery

The Painscreek Killings
Shared: Mystery · Horror · Investigation

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