Sad Satan is a very strange game built with the Terror Engine. It was first reported on the YouTube channel Obscure Horror Corner, and the channel's owner claimed that he had downloaded it on the Deep Web.
Currently, there is no way to confirm the origin of the game. It was alleged that a Deep Web user under the name of "ZK" made the game, but it was also speculated that the owner of Obscure Horror Corner created it just to gain attention.
There are two games very similar to Sad Satan, made by Indie BD user "NameIess": Evil and FUN. However, these games are not spiritual successors as they were released prior.
Why It Sucks
It doesn't even qualify as a video game. It is just a walk simulator made to be disturbing, and in fact, it is even more disturbing than Demonophobia for comparison. The "game" is just walking through monochrome corridors, hearing distorted audios from real world serial killers, and seeing some pop-up real photos of child abuse, gore, and other (really unsettling) things. There are some idle children on the corridors, and eventually, one of them will attack and kill the protagonist, effectively finishing the game for good.
To make matters worse, someone claiming to be its developer released a malware version of the game on 4chan, saying it was a "full uncensored version" of the original one shared by Obscure Horror Corner. Numerous users had their computers becoming unresponsive or not booting properly after trying to execute that "full version" of the game.
Many theorize that child abuse is the main theme of the game and worst that Sad Satan is more of a Snuff Movie than a game
The Only Redeeming Quality
The game, thankfully, is now illegal, so people won't suffer anymore.