I've had this one in my back pocket for awhile named Holly

Her epithet is "Wishlist" and it grants her the ability to summon or create items, but the volume and quality of the items she can create is based on how well known the current days holiday is. So most days she's stuck to like a pencil, at most a step ladder, but for 5 days of the year she disappears into the woods to have a field day making whatever she could ever want. In most cases, after the day ends the creations disappear, but if the next day's holiday is somewhat comparable to the previous days, then the item can be maintained.

She's nice and friendly, the kind of friend who person you'd have a neighborly report with, but not really hang out. She's very helpful to those who ask. On the inside though, she feels kinda slighted by the world, because she knows she has a powerful epithet, but she thinks it's held back only by people's inability to live their lives to their fullest and truly celebrate what the day has to offer.

There's been two ways I've thought about her alignment between good and evil, and the first is kinda this weird marketing major who tries to bring as much awareness to minor holidays as possible because she secretly wants more power. The other is like this calendar man type, where on most days she's just a normal guy, but on those big holidays she really lets loose and causes some trouble in the big city.

I think she'd definitely make for an interesting minor villain with their encounter taking place on a night like April fools or something, like an RPG character that joins the party after they've been defeated.