Mercedes and the Waning Moon: The Dungeoneering Feats of a Discarded Vampire Aristocrat officially has an anime project in development. No details regarding the adaptation were revealed.

Mercedes and the Waning Moon: The Dungeoneering Feats of a Discarded Vampire Aristocrat is a light novel series written by Firehead and illustrated by KeG. It began on Shosetsuka ni Naro before being picked up by TO Books, which began publishing the series in May 2021. Three volumes have been released as of February 2022.
There is also a manga adaptation by Pochi Edoya, which was launched on TO Books’ Corona EX website in August 2021. J-Novel Club licensed the novel in English, describing the story:
Reincarnated as a vampire to a noble father and his shunned concubine, Mercedes Grunewald has always known that one day, her father will choose an heir that isn’t her. But what will become of her family when that time comes? Her mother has no skills, their maid is old, and Mercedes is but a small child. How will they survive in the world on their own? Luckily, dungeon crawling is a job that anyone can do—even a child. To provide for her family, Mercedes begins training at the age of a kindergartener, and because she’s from a nation of vampires, she fortunately has the potential to become strong. In her past life, she died unfulfilled, but that won’t be her fate this time. In the dungeons, she’s determined to find something that will make her moon full.
Source: TOBOOKS Official X
© Firehead, KeG, TOBOOKS