The game takes place after The Beginning of the End downloadable content from Episode 3, as the world has been destroyed, but that doesn't stop Tycho and Gabe from having to return to the moral plane from Underhell.
As with Episode 3, the game is developed by Cthulhu Saves the World studio Zeboyd Studio, and also features a new music score from HyberDuck Soundworks, which also did the scores to Dust: An Elysian Tail and Scrolls.
The game will also be appearing "soon" on Xbox Live Indie channel as well. It costs $4.99 USD on Steam, with a 10% discount in its first week of release. The Xbox 360 version will cost 400 Microsoft Points.