In a new legal filing, Epic Games argues that Apple is threatening its entire ecosystem with its belligerent behavior. And it has the backing of Microsoft.

The new filing is just the latest development in the quickly escalating saga of Epic v. Apple, in which the former company alleges that Apple is abusing its dominant position in mobile and behaving in an anti-competitive fashion. Apple has attacked Epic, in turn, for violating the terms of its developer contract and is threatening to pull Epic and its Unreal Engine out of its App Store, a move that would damage many, many game developers.

“Over the past week, multiple Unreal Engine licensees have contacted Epic expressing grave concern over Apple’s actions and its impact on their iOS and macOS-bound projects,” the legal filing notes. “Epic submits herewith … a declaration from the General Manager of Gaming Developer Experiences at Microsoft addressing this issue.”

“Kevin Gammill, Microsoft’s General Manager of Gaming Developer Experiences, attests that there are ‘very few other options available for creators’ that offer ‘as many features and as much functionality as Unreal Engine across multiple platforms, including iOS’ and that Apple’s revocation of developer tools ‘will place Unreal Engine’ and games that use it ‘at a substantial disadvantage,” the filing notes.

“Mr. Gammill also explains that ‘Unreal Engine’s sudden loss of support for iOS and macOS would create significant costs and difficult decisions’ for game creators, who ‘would have significant sunk costs and lost time using Unreal Engine for game creation, and would have to choose between (a) starting development all over with a new game engine, (b) abandoning the iOS and macOS platforms, or (c) ceasing development entirely’.”

Microsoft, of course, has its own issues with Apple and its unfair App Store licensing policies. The software giant will soon launch an Xbox Game Pass streaming app on Android, but it is unable to do so because Apple’s rules forbid any game app from offering multiple titles, as would Microsoft’s. Apple says that it would need to examine each game the app offers in order to protect its users from abuse, while Microsoft counters that there are already rating boards that provide this service in the game industry.

Tagged with App Store, Epic Games