Need help with Lore for a new home-brew race

[Ghostwidow]

So, I am attempting to implement a new race into my homebrew campaign. A dark fey/sprite/faerie type creature. Basically a cursed/fallen fey the got banished to the shadowfell and lost its wings, but in place grew a tail and obtained darkvision. I already have the appearance and abilities worked out, just need a lore/background for it. I know it sounds very Maleficent, but im leaning more towards the differences between drow/surface elf..grey dwarf/surface dwarf…deep gnome/surface gnome, etc. However, I am trying to come up with something that differs from the lore of underdark vs surface world races. This is where im getting stuck and need help.

[Abracadangit]

While I don't know that I'd have any concrete ideas, here are some questions to jog your creativity neurons:

1) Why were they banished in the first place? Was it because of some grave sin they collectively committed as a people, or was it more like their king/queen/ruler did something bad, and all their subjects were banished as a result?

2) What have they been up to since their banishment? Are they all practicing shadow magic and dark arts now, or do they largely eschew those things, afraid they might be lured to dark paths if they did?

3) How do they feel about their not-banished cousins? Is there ill will, a thirst for revenge? Or maybe the banishing incident wasn't even the light fey's fault, so there's no bad blood.

Hot take -- maybe instead of being banished, they willingly went to the Shadowfell to seal some great evil, to learn its magic as a weapon against some cosmic threat, etc. Of course, if you prefer the banishment angle, I understand -- just throwing ideas out there.

I'd think about the answers to these questions before trying to hammer out specific lore -- get a feel for the people, what they're about, how they feel about their predicament. Then circle back around and fill in the "whys" to those answers with the lore.

They sound really cool -- best of luck!