With so many different knobs and dials to turn and levers to pull in Age of Sigmar, there's an infinite amount of fine-tuning that can be done to the game in order to make it run as smoothly as possible. To help that along, Games Workshop has announced Battlescroll.
From the article:
The Mortal Realms are home to many creatures, from the lowliest grots to living gods. There are plenty of interesting new dramatis personae popping up every year, and as the game evolves to include new factions and rules updates, the designers want to ensure that it remains fun and fair for everyone.
While the rules team is happy with the general state of affairs, they’re constantly looking to make sure that every army feels fair and enjoyable to use. This is especially important in Matched Play where small changes can affect the balance of the competitive environment.
With this in mind, present and future Warhammer Age of Sigmar updates will be collected into downloadable booklets called Battlescrolls. These gather rules changes, points changes, and other tweaks into a simple, easy-to-read format, preventing you from having to wade through hundreds of pages of information.