Games like Beastiarium
Games like Beastiarium include Stray, Poppy Playtime, Bendy and the Dark Revival, Little Nightmares II, and Little Nightmares. We matched them by the tags players give Beastiarium on Steam (Indie, Adventure, Horror, Atmospheric, and Puzzle): closest matches first, and among equally close ones the better-known games.

Stray
Shared: Adventure · Atmospheric · Puzzle

Poppy Playtime
Shared: Horror · Puzzle · First-Person

Bendy and the Dark Revival
Shared: Horror · Adventure · Indie

Little Nightmares II
Shared: Adventure · Horror · Puzzle

Little Nightmares
Shared: Horror · Adventure · Atmospheric

Hello Neighbor 2
Shared: Adventure · Horror · Puzzle

Outlast
Shared: Horror · Atmospheric · First-Person

We Happy Few
Shared: Adventure · Indie · Action

Among the Sleep - Enhanced Edition
Shared: Indie · Horror · Adventure

Amnesia: Rebirth
Shared: Puzzle · First-Person · Horror

Spooky's Jump Scare Mansion: HD Renovation
Shared: Indie · Horror · Adventure

MiSide
Shared: Horror · Cute · First-Person

Bendy and the Ink Machine
Shared: Horror · First-Person · Puzzle

The Room
Shared: Puzzle · Atmospheric · Adventure

Five Nights at Freddy's: Secret of the Mimic
Shared: Horror · Adventure · First-Person

LIMBO
Shared: Indie · Puzzle · Atmospheric

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

The Hat Man: Shadow Ward
Shared: Indie · Horror · Adventure

The Room Two
Shared: Puzzle · Atmospheric · Horror

Penumbra Overture
Shared: Adventure · Horror · Indie

The Forest
Shared: Horror · Adventure · First-Person

Atomic Heart
Shared: Adventure · Action · Horror

Firewatch
Shared: Adventure · Atmospheric · First-Person

Lethal Company
Shared: Horror · First-Person · Atmospheric