gatekeeper

noun6

1. •
   A person who guards or monitors passage through a gate.

   • […]“Here,” he said, stepping forward and handing twopence to the gatekeeper; “let the young woman pass.” — 1874
2. •
   In dissociative identity disorder, an aspect of the personality that controls access to the various identities.
3. •
   One who gatekeeps.
4. •
   A provider of core platform services with specific characteristics (Regulation (EU) 2022/1925 of the European Parliament and of the Council)
5. •
   (figurative) A person or group who controls access to something or somebody.
6. •
   A common orange and brown butterfly with eyespots, Pyronia tithonus, of the family Nymphalidae.