Why would an APK contain DLL files?
Izzy's guess is correct. Unity is based on Microsoft's .NET programming environment. A Unity game is written in C# and compiled to DLL files (the portable executable format, which is abbreviated to PE32 in the output you included). Unity packages those files along with the game's assets (3D data, textures, videos, sounds, &amp;c.) and the Mono runtime. Mono is an open-source runtime for software made in .NET: it loads the .NET DLL files and executes them.

DLL files can contain executable programs for Windows, or Windows icon files, or compiled .NET code (the .NET equivalent of Java .class files). In a Unity game, it's the last of these options.