BloodRayne developer Terminal Reality and its exclusive licensee Infernal Technology are suing Microsoft for infringing on the patents for its lighting and shadowing technologies.
While primarily known as a developer, Terminal also created a variety of game engines, including the Infernal Engine that's at the heart of this case.
According to the complaint (as spotted by Patent Arcade), Terminal believes a number of Microsoft titles and the engines used to create them have infringed on its Infernal Engine tech patents.
The list of infringing titles includes big names and recent releases like Halo 5, Gears of War 4, Sea of Thieves, and PlayerUnknown's Battlegrounds.
Although its currently at loggerheads with Microsoft, Terminal hasn't been active in the world of game development since reportedly shutting down its Texas studio back in 2013.