Thank you all for your ideas.
Ok, so Mother Night is a bit more unpleasant than I was thinking. Shar is a very good analog. With some Wee Jas and Raven Queen. Still, I'm not making her outright evil.
The Dark Powers as its source could work, but I haven't thought much about them and honestly I'm not really that interested in them.
The Blessing of Mother Night will consist of:
- Her hair will become frizzy and grey, like an old woman's;
- Her weapons become Vicious Weapons. That is, they become magic attacks with extra damage on a crit;
- As an action, she can touch another creature to transfer the Vicious attacks to them. Only one creature can have the vicious attacks;
- Werewolves recognise that she has been blessed by Mother Night. They won't be hostile towards her and her allies;
- When in melee combat, the vicious attacker must make a DC 13 Charisma saving throw, every turn. If she fails she must use her bonus action to bite one enemy (13's not that difficult, she's a Bard). The character is proficient with the bite, it deals 1d4 damage and is also magical and vicious.
See, I don't want to make it that good. I like how Curse of Strahd is a low magic campaign and I resent that this player used her gamer knowledge to try to sneak in extra power into her character, while everyone else is a beginner and following the normal rules. She's very experienced and often uses player knowledge to fight monsters and stuff.
Although, in her defense she kind of expects the blessing to fall on every party member... And the drow been dancing naked outside in the cold for more than a week already.
She doesn't have any magic weapons yet, so that's a cool way to giver one anyway. With a bit of a cursed blessing.
EDIT: This player also DMs, and from what I heard about her games it seems like she enjoys empowering her players, like, a lot.
