I'm looking for novels including fan fiction where the MC has a secret lair(s). Better yet if the lair can be accessed through a hidden entrance. Also be cool if they can access it easily from home, work, or school.
When you say secret lair, you mean like a cave or a secret room? Not a interdimensional space or some such?
Correct, I'm not looking for dimensional/spacial pockets where the MC can enter at any time or place. I'm talking about something like a batcave or a hidden basement/floor. It can even just be a small hidden room. Warehouses and things too that act as lairs are fine too. I'm also fine with a lair that has the properties or security of being hidden via dimensional or spacial shenanigans so long as the MC is still forced to go to fixed locations to access it. So like a lair entrance anchored to a specific allyway hidden in the gap between spaces and only accessible by passing a special dimensional membrane/barrier is fine. Or like a door that normally leads to the other room, but knocking on it a certain way transforms it into a magic portal to a secret lair hidden in a pocket dimension. I'm also looking for hidden stashes so something like the superhero MC is able to install and access a hidden closet space behind the his locker at school that is open through a hidden fingerprint scanner in the locker and stashs emergency gear .
Poison Genius Consort Divine Doctor: Daughter of the First Wife I will add more if I remember and have time.