Glitch

>Assists Selen in his horror merch shop
>Also wearing a costume but there is something fishy abouts her nobody can put their finger on...
>Nobody can remember when or how she joined the lair, it's as if she's always been here
>as everybody seems to remember she's always been here nobody questions it either

More lore notes:
She resembles an uncanny ghost and her true self should stay a mystery. It's unclear what her intentions are or if there actually are any. It could be hinted at that her appearance and Selens obsession with one of the two eldritch guardian dragons are related but it's not neccessary, maybe that's also a coincidence (this lair is a haunted place after all, so ghosts and other supernatural appearances are part of the daily life).
Glitch mostly works from the attic at Selens little merch/costume/halloween shop where the wares are stored so she doesn't have to talk too much to customers (her voice can be really unnerving, she repeats random words a lot and sounds like a broken record). All other dragons don't suspect there could be something wrong with her, they just assume she's a shy and awkward dragon with some talking problems (some kind of magic is in place here as any dragon not affected by it would clearly see how unnatural Glitch moves (for a lack of a better comparison, it looks like as if her idle animation has a few frame drops every second / her movement stutters just like her speech. Sometimes she appears to clip into solid objects as well). Although she should be rather clumsy due to her movement restrictions she still does a fantastic job with the wares (it appears as if her many arms clip through the objects she handles but some kind of invisible force holds them in place nonetheless)
Glitch herself appears to be colorblind, although Selen suspects she might be able to see the color red from time to time.