Bios files are essential system files that are required for Lemuroid to function properly. They contain the firmware that allows the emulator to mimic the original hardware of classic gaming consoles. Without bios files, you won't be able to play many classic games on Lemuroid.
The only entirely legal way to acquire BIOS files is to dump them directly from a physical console that you personally own. This process involves: lemuroid bios files free