The First Descendant
24 Achievements
57-69h
Steam
Knock, Knock! Who is it?
Complete all available missions and Descendant duties in Vespers
29.8%
How to unlock the Knock, Knock! Who is it? achievement in The First Descendant - Definitive Guide
Story related and can not be missed.
Note: For some reason there are only achievements tied to the first three zones in the game's campaign. You'll need to continue the story to unlock the other areas to get crafting materials and continue to level up your character and account Mastery though, so be sure to finish all the zones.