Start Terminal.app and type:
sudo nvram boot-args="kext-dev-mode=1"
Verify that command works by typing:
sudo nvram -p | grep -i boot-args
You should see a line:
boot-args kext-dev-mode=1
Now reboot. If you plug in your razer stuff after the reboot you should see the following in Console.app:
19/09/14 11:12:05,837 com.apple.kextd[19]: kext-dev-mode allowing invalid signature -67023 0xFFFFFFFFFFFEFA31 for kext "/System/Library/Extensions/RazerHid.kext"
@name153, This "fix" disables a part of macOS's built in security. Specifically, the part responsible for preventing malicious kernel extensions from being installed. A kernel extension (or kext) extends or otherwise modifies low level parts of the operating system. Enabling kext-dev-mode allows any kernel extension to be installed, not just those with valid certificates issued by Apple.