That mask existed purely for the dramatic face reveal. The reason the elf queen wasn't wearing a mask is because the story didn't include any interactions between her and the human kingdom.
I get that the story got axed... but dang, that was kinda painful to read. Not the TL quality to be clear, thank you for translating. No, I mean the story itself and the way the fight played out. It's just a #feelsbad moment.
it's super sad that we got a nice idea with this series and the start was good, I think getting rid of the comrades so soon in the story was a bad idea in the end, after that we got really poor amount of good moments, but the alliances were a good idea, sadly their were always too OP, so most battles didn't felt like they had stakes.