Games like Castle Forbidden
Games like Castle Forbidden include Poppy Playtime, Little Nightmares II, Outlast, Little Nightmares, and MiSide. We matched them by the tags players give Castle Forbidden on Steam (Horror, Adventure, Multiple Endings, Singleplayer, and Psychological Horror): closest matches first, and among equally close ones the better-known games.

Poppy Playtime
Shared: Horror · Singleplayer · Puzzle

Little Nightmares II
Shared: Horror · Adventure · Singleplayer

Outlast
Shared: Horror · Psychological Horror · First-Person

Little Nightmares
Shared: Horror · Adventure · Singleplayer

MiSide
Shared: Horror · Psychological Horror · Singleplayer

Amnesia: The Dark Descent
Shared: Horror · Psychological Horror · Puzzle

Resident Evil 7 Biohazard
Shared: Horror · Singleplayer · First-Person

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

Five Nights at Freddy's: Security Breach
Shared: Horror · Singleplayer · Multiple Endings

SOMA
Shared: Horror · Psychological Horror · Atmospheric

Layers of Fear (2016)
Shared: Horror · Psychological Horror · Singleplayer

Outlast 2
Shared: Horror · Psychological Horror · Singleplayer

Fran Bow
Shared: Horror · Psychological Horror · Adventure

Garten of Banban
Shared: Horror · Singleplayer · Psychological Horror

Scorn
Shared: Horror · Atmospheric · Puzzle

Hello Neighbor 2
Shared: Adventure · Horror · Puzzle

Sally Face - Episode One
Shared: Horror · Psychological Horror · Adventure

Escape the Backrooms
Shared: Horror · Psychological Horror · Adventure

INSIDE
Shared: Horror · Atmospheric · Singleplayer

Inside the Backrooms
Shared: Horror · Psychological Horror · Puzzle

Amnesia: Rebirth
Shared: Horror · Singleplayer · Puzzle

The Room Two
Shared: Horror · Puzzle · Adventure

The Room Three
Shared: Adventure · Puzzle · Singleplayer

Bendy and the Ink Machine
Shared: Horror · Singleplayer · Puzzle