Celestial Elves must keep their blindfold on, lest they accidentally see their Archdragon and lose their sanity to the horror of a Star Devourer Dragon.
The chances of anything like happening is near zero, but I personally theorize Aaravos to not only be a Star Devourer Dragon, but also the Archdragon of the Stars - The Star Scraper is the Star Nexus, and Aaravos's key unlocks both the Nova Blade and the Corona of the Heavens.
...This artwork is going to become so incredibly dated when Season 6 comes out - I had to make up colors for the Star Scraper and colors for the older Celestial Elves outfit.
TBH I thought "why did he have to say it like that" anytime Aaravos said or did anything. I also didn't want to do lineart so please don't mind the messy sketch