roleplay related question/concern my idea would break lore

So my idea and style of roleplaying is more anti-hero or anti-villian with an alignment around chaotic/neutral.

I was thinking about saying story wise/lore wise for my character that she is an lalafell who became cursed to feed upon life force after commiting some magical crimes in the past. aka like a vampire feeding upon idk aether of living people or something and that I was awakened by a scion accidentally and was given an option of working for them doing so called good or remain in her prison sealed away (sorta like a velvet crow from tales of berseria story line for her)

Welcome to Eorzea! (I would have welcomed you in that other thread but sadly it was destroyed by trolling).

As for your question - lore wise there are creatures that feed on aether in Hydaelyn, and specifically, this is the fundamental aspect of voidsent, although why they are like that and what they really are is a big spoiler you haven't reached yet, so I won't spoil it for you (also, in the current expansion there is a certain boss during a raid that is virtually a vampire, but feeds on aether not blood, but he has all the imagery - right down to the fangs :D) And to say nothing of a certain woman in the current storyline.).

Either way, if you want to roleplay your character as an aetheric vampire, then that is perfectly fine! It's entirelly up to you! :D

There's also a totally-not-vampire in the red mage job quests (technically he feeds on aether, but he has to draw blood to access it first, so the symbolism is there).

As for if it's too special or anything, do not worry to much about others strict views on what is allowed to be RPd or not..,
Hope you enjoy yourself in Eorzea and etc..,

The story has enough wiggle room, and the lore has enough open ended gaps for the Player Character.., <Outside of SE barring anything extremely evil..,>

<So yes, even for those Au Ra Dragoon RPs out there, enjoy yourself..,>

You could play a descendant of mhach with voidsent blood in their veins. Since you seem to be already Lalafell, which are naturally descendants of mhach, it would be probably not that far fetched. I mean you will be still the most unique snowflake among them all but at least with a little tiny bit of canon lore! And with voidsent blood you can go as edgy as you want, voidsents are literally vampiric creatures so that would fit right into your concept.

But in the end, just play what makes you happy.

Edit: And don't forget your sidekick, every Velvet needs a Laphicet.

Find yourself people who mesh with your narrative idea. If group is in same wavelength like that, little lore can be easily bend with nothing really breaking and all the fun to be had.

Ranaku's idea seems like something I would borrow/remix/steal if Velvet kind of character was my objective (｡•̀ᴗ-)✧

Another good idea is to have your WoL live in a cage