From the Crosshair VIII Extreme manual: "8 System Agent initialisation after microcode loading" (although that's for a newer board, codes tend to remain roughly the same for the same CPU and board extended families).
Microcode is the hidden software that runs inside the CPU, managing more complicated functions and executing the more complex opcodes/instructions. It's kinda the secret OS hidden inside your CPU, and it's basically failing to boot or getting stuck there (that's what the code is saying). The BIOS is part of the picture there as well, for the CPU's internal boot sequence.
Have you tried removing the motherboard's battery for a short while, to completely reset the board? It's the CR2032 button cell battery which often lives somewhere near the bottom/south edge of the board. You should probably drop a new battery in after giving the board some quality no-power nap time (give it a minute or 5 with no battery), then clear CMOS as the first thing (removing the battery kills the data stored in CMOS, but you want to get it back to the clean state which comes from the actual clear procedure). It may be hidden under the removable shroud around the lower PCIe slots. Someone on reddit had a very similar problem to yours and the battery was the fix:
Try reading this thread.
It's a Crosshair VI, but it's the same.
Probably a CPU problem.
I would try removing the CPU and reinserting it.
I am not able to remove the CPU without removing the water block, and I do not have the thermal pads needed to replace once the seal is broken. I also don't see how it can be CPU related when it was working fine before I moved the motherboard to the new case. I did not touch the water block or CPU, therefore, in theory, nothing has changed.