1. Your battery level is below 3.68 V (3680 mV) (about 10% charged).
2. You have a custom recovery on the recovery partition AND a custom ROM on the system partition.
3. You have just re-locked your bootloader and you can't re-unlock it because your battery is too low (less than 10%).
Here's the problem: If you want to use a RUU, you need about 30% battery. But, if you have less than that, you need to charge it. But the problem is, you can't charge it because you can't boot your phone into either recovery or the ROM itself in order to accept a charge. A re-locked bootloader will NOT allow you to boot either into the custom recovery or the custom ROM. And, you cannot charge your phone in fastboot. Additionally, you cannot re-unlock your bootloader because your phone has even less than 10% charge (3.68 V). If you have between 10% and 30%, then simply re-unlock your bootloader and boot into recovery and charge as normal to a level somewhere above 30% if you want to flash an RUU. But, if your battery is below 10%, then you will need to bring it back above 10% with the script below.
So you need the following script which power cycles your phone repeatedly in order to turn off your screen long enough to accept a charge. Once you reach 3.68 V, which is 10% charge, you're through the woods, so to speak, as you can then, re-unlock your bootloader.
Run the following script as a batch file while your phone is in USB fastboot mode.
Here is the script:
" @echo off :start fastboot getvar battery-voltage fastboot reboot-bootloader ping /n 6 localhost >nul goto start "