Arlecchino may be the harbinger we know the least about, and that's kind of why I've held off on making any concrete theories about her... until now.
After my deep dive into the historical inspirations for Fontaine, I finally have some fresh thoughts to share! So c'mon in, and let's get to know Arlecchino, the Knave.

*Timestamps*
No timestamps; watch the whole thing. It's short. Ish.

*More Information*
This section is a combination of citations and terms/topics that came up during the video alongside their wikipedia articles (or similar related sources) which should help get you started when doing your own research.

Arlecchino: https://genshinimpact.fandom.com/wik...
House of Hearth: https://genshinimpact.fandom.com/wik...
Angel Ranks: https://en.wikipedia.org/wiki/Angel
Seraph: https://en.wikipedia.org/wiki/Seraph
Cherubim: https://en.wikipedia.org/wiki/Cherub
Hand of Glory: https://en.wikipedia.org/wiki/Hand_of...
Melpomene Mask (Sock and Buskin): https://en.wikipedia.org/wiki/Sock_an...

WWI Oversimplified:    • WW1  Oversimplified (Part 1)  
Crash Course European History WWI:    • Who Started World War I: Crash Course...  
Simple History WWI:    • The Bullet that Started WWI  
WWI: https://en.wikipedia.org/wiki/World_W...
Concert of Europe: https://en.wikipedia.org/wiki/Concert...
Young Bosnia: https://en.wikipedia.org/wiki/Young_B...
Franz Ferdinand: https://en.wikipedia.org/wiki/Archduk...
AustriaSerbia Relations: https://en.wikipedia.org/wiki/Austria...