Chosen Solution
I recently bought this mac, and I wanted to factory reset it. While it was rebooting, I accidentally unplugged it and the screen has not turned on since. I tried to do a PRAM reset, but it did not respond. I have tried to make a bootable disk, but that dod not work either. The fans spin and I think the magic keyboard connects to it but the screen stays black.
See if you can boot up in Safe mode, press Shift (⇧) key during startup Reference: Mac startup key combinations If that fails time to visit an Apple Store
Try using a wired USB keyboard (any will work), The driver for the magic keyboard probably is not loading. Then try rebooting in Recovery Mode and run Disk Utilities.
