Telltale Games, who are best known for their choice based graphic adventure games, such as The Walking Dead, The Wolf Among Us, and Batman, have been using the same engine since 2004. It’s called the Telltale Tool, and it was developed to facilitate Telltale’s brand of storytelling.
Telltale has made additions to the engine over the years, but it was old and getting creaky, straining at the seams- which you could see in just how buggy and unstable their newest releases had been. Now, almost a decade and a half since the engine was introduced, Telltale will be transitioning away from it to Unity.The company has confirmed that The Walking Dead: The Final Season will be the last game to use that engine, with The Wolf Among Us Season 2 and Stranger Things both being built on Unity instead.
This bodes well- while Unity has its own set of problems, especially on consoles, it’s a more modern engine, and it is better supported. Hopefully this means good things for Telltale’s games.