METALIAM made a great overview of the Alcest & Peste Noire legacy:
Alcest was born as a raw Black Metal band and then moved to more "dreamy" atmospheres, while remaining an underground band.
You can check it out on Youtube their material as suggested by METALIAM, you will be surprised by their change in music style :-O
The same musicians (more or less) were involved also in the bands "Amesoeurs" and "Les Discrets"
(the first one unfortunately split after the first album).