She gave me both names and said I could call her Sere. That does sound like something bond worthy.
They appear and we can add runes when needed, like a rune for glamouring normal humans. Most Shadowhunters though have at least one permanent rune though that marks them as such.
I've spent my entire life training on how to be a Shadowhunter. I've yet to kill an actual demon but I've helped in delivering their deaths. Demons are not something to be trifled with by anyone. I'll do what I can to keep you safe though.