Tom Jubert, one of the co-writers on the main game, together with Jonas Kyratzes, wrote a blogpost about his work on The Talos Principle DLC "Road To Gehenna"!
Here is a snipet:
Without spoiling anything, the pitch we went with provides us huge flexibility in terms of the sort and tone of material we deliver. It gives us a world that fits within the original game's religious and science fiction mythology, but which resolutely has its own identity. Most importantly for me, it lets us explore completely new ideas about how to interact with the game.
Read whole blog post by Tom Jubert and find out more on this link.
In "Road To Gehenna" all pieces seem to fall into their place perfectly, like Sigils on the board! We'll have very exciting DLC in the near future!