Outlast

Outlast does one thing and does it relentlessly: it makes you run away and find somewhere to hide and then makes that hiding place feel insufficient. The asylum setting, the night-vision camera mechanic, the complete absence of any means of fighting back. It is not a rounded game in the way the top entries on this list are rounded. But as a pure fear delivery system it remains effective more than a decade after release. It is more limited in design depth than anything in the top ten, which is why it sits here rather than above Signalis or SOMA.

Outlast does one thing. You cannot fight back. You run, you hide, you film everything on a camcorder with a night vision mode that becomes your only source of light in the darkest sections of the game. It is a pure panic delivery mechanism and it is still effective more than a decade after release. The reason it is here rather than in the top ten is that it is narrower than its competition. There is no systemic depth, no resource management, no philosophical weight. Just fear. On Steam Deck it runs well and the controls map cleanly. If the concept of being completely helpless in an asylum appeals to you, Outlast remains one of the cleanest examples of that specific kind of horror.