Microsoft announced the release of the Windows 11 Insider Preview Build 22518.1012 update for the internal testers of the Dev channel on December 11, 2021. This version (KB5009380) does not bring new features because it is just cumulative update of Build 22518 that is released two days ago.
According to Microsoft, build 22518.1012 (KB5009380) is aimed to test the service pipeline in the Dev channel, so it will not bring new features.
Windows 11 Insider Preview Build 22518 which is released on December 9, 2021, is of course a fairly large version with new features and improvements.
The new features in build 22518 include Spotlight collection of desktop background wallpapers, voice access, new entrances to widgets in the taskbar, and so on. With Spotlight collection, you can enjoy lots of background wallpapers every day. And the new feature voice access will allow you to interact with your computer by voice. click here to learn more details of Windows 11 Insider Preview Build 22518.