Is it because he's a scribe? Is it law if you are the last Eliksni of your house, you have to wear a veil over your rebreather?
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Probably just a fashion statement, honestly. Either that or it has some kind of significance, like how Hunters have their cloaks [i](speaks to their personality)[/i], and Titans have their marks [i](references their deeds and influence)[/i].