Games like Tantalus
Games like Tantalus include The Exit 8, Prey, Platform 8, The Cabin Factory, and SOMA. We matched them by the tags players give Tantalus on Steam (Immersive Sim, Sci-fi, Space, Walking Simulator, and Psychological Horror): closest matches first, and among equally close ones the better-known games.

The Exit 8
Shared: Immersive Sim · Walking Simulator · Psychological Horror

Prey
Shared: Immersive Sim · Sci-fi · Space

Platform 8
Shared: Psychological Horror · Walking Simulator · Immersive Sim

The Cabin Factory
Shared: Immersive Sim · Walking Simulator · Psychological Horror

SOMA
Shared: Sci-fi · Psychological Horror · Horror

ROUTINE
Shared: Sci-fi · Psychological Horror · Walking Simulator

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

Mouthwashing
Shared: Psychological Horror · Horror · Walking Simulator

Lethal Company
Shared: First-Person · Sci-fi · Horror

Observation
Shared: Space · Sci-fi · Psychological Horror

There Exists Nobody
Shared: Immersive Sim · Walking Simulator · Psychological Horror

Outer Wilds
Shared: Space · Sci-fi · Horror

Kiosk
Shared: Immersive Sim · Psychological Horror · Horror

Alien: Isolation
Shared: Sci-fi · Horror · Space

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

POOLS
Shared: Walking Simulator · Psychological Horror · First-Person

MiSide
Shared: Psychological Horror · First-Person · Horror

Dreamcore
Shared: Walking Simulator · Psychological Horror · First-Person

The Boba Teashop
Shared: Psychological Horror · Walking Simulator · Immersive Sim

KARMA: The Dark World
Shared: Walking Simulator · Psychological Horror · Sci-fi

Iron Lung
Shared: Psychological Horror · Horror · Sci-fi

Who's at the door?
Shared: Immersive Sim · Walking Simulator · Horror

Dollmare
Shared: Psychological Horror · 3D · Horror

Moons of Madness
Shared: Sci-fi · Space · Horror