The mf.dll file is one of the system DLLs used by Windows Media Player. Overwolf relies on this file (and others like it) to record videos properly.
However, Windows N editions do not include Windows Media Player by default, which means the required DLL files, such as mf.dll, are missing from the system.
But don’t worry, we’ve got you covered!
You can restore these missing files by installing the official Microsoft Media Feature Pack for your version of Windows: