although it's described as looking like it was always meant to stand where it does right now. Its master has the power to manipulate fate, so it's possible that it was fated to end up in Gensokyo
Remilia wreaked some havoc for a while right after showing up, but was beaten back by other, more powerful youkai in other factions for threatening their delicate balance
The vampiric need to feed on humans and the human village's need to have alive humans and the general youkai populace's need to terrorize humans came to a head after a few years of rising tensions
While she's human, there's a lot that's mysterious about her. Her age is unknown, and while she looks to be a teenager, she's described in-setting as having the mannerisms of someone much older
Her ability to manipulate time extends to, in accordance with quantum physics, manipulating space as well. Because of her powers, the mansion is larger on the inside than it is on the outside.
It's also been ICly speculated, interestingly, but not confirmed, that the second reason for the Scarlet Mist Incident was to get Sakuya to meet other humans and learn that she can still connect with them.
Meiling's most exciting adventure was the time she battled an evil god of earthquakes, although she was dreaming the whole thing after reading too much manga
A terrifyingly powerful super-vampire with the power of absolute destruction - She can draw out the "eye" of any object, pull it into her hand, then crush it, causing the object to be destroyed.
on the list... Eientei, Youkai Mountain, The Underground, Myouren Temple, The Taoists, The Lunar Capital, The Beast Alliance, Human Village, Fairies...
(Dragons in Touhou don't, like, actively exist in any place you will ever see them; ZUN has mentioned them in passing as the only beings that may actually surpass gods in power but I'm pretty sure we've never seen one and never will)
ZUN like "well they started treating the generically named midbosses like characters, so I started giving midbosses names, and people kept making up backstories for them, so I started giving them backstories" and now there's a midboss who's the secret instigator of the plot
)she's a Chinese martial artist, so that should have been 100% given