"The Stanley Parable", a first person exploration game has been available for quite some time, and its safe to assume that it's already stable and bug-free. Sadly, co-creator of the game, Davey Wreden explained that a black monolith that appears at the conclusion of a mini-game is not meant to be there, according to a post in galactic-café.com.

While Wreden was developing the game, someone from his team thought that it would be funny if include a mini-game where you have to do several hours of tedious work, which is really boring, and the game will ask players to do it for four hours. That thought gave birth to the mini game. The mini game is about a baby that crawls from end to end, into a fire and to save the baby, a button should be pressed to delay the baby's death for a few seconds, over and over again. 

The developers safely assumed that no one will do this, but if someone will be able to finish it, Davey Wreden placed a short message about "the essence of divine art" at the end of the mini-game. Naturally, players did it and saw the message, also the black monolith, which implies a sense of vague mystery. However, the monolith is a bug and is just the remains of a sliding door that got past quality control staff because nobody really tested it.

The monolith is not the actual problem but it covers some parts of the message at the end of the mini-game. Since it is a bit late to make the effort of players who persevered to finish the game meaningful, Davey Wreden says he could at least make the message legible. The upcoming update will remove the monolith to make the full message visible.

Instead of spending several hours of playing the mini-game, of keeping the baby crawling into a fire, the full message is at the game's Wiki page.