Fallout: New Vegas developer Obsidian Entertainment is teasing a new game on its official website.

The front page of the site contains an image of an Ouroboros surrounding a number that is counting down at the rate of one every day. It will reach zero this Saturday.

Below the counter is some text:

"The book unread is unwritten. The reason we don't explain it is the reason we use it. Its power is in its mystery. That is the Leaden Key, in part, in whole. Is it clear? Digging for truth buries the seeker."

Within the page’s source code are more clues:

"Two centuries ago, your divine champion told the people of Dyrwood to grovel at his feet. If you've come on pilgrimage to the blasted crater that was our reply, Godhammer Citadel is *that* way.

"X . X X . X X To tenderness, fellowship. To fellowship, vigilance. So bring we all to the Night Market. I am the Spindle of Esenath. Know me by my light and stand with me in darkness."

Clicking on the counter takes users to a forum for speculation over what is dubbed “Project X” – “Obsidian's next RPG endeavor”.

Our guess is Half-Life 3.