“Amok Time” undoubtedly ranks first among TOS episodes revealing details about Vulcan culture & biology & about Spock himself. Other such episodes include
“The Enemy Within” (first use of Vulcan nerve pinch), “Dagger of the Mind” (first use of Vulcan mind-meld),
“Balance of Terror”
(revelation that Vulcans are related to Romulans), “Journey to Babel”
(introduction of Spock’s mother & father & relation of some of Spock’s back-story), & “The Savage Curtain” (introduction of Surak & relation of some
Vulcan history/philosophy).
“Amok Time” features the first of three TOS-era Vulcan matriarchs who preside over religious/mystical/philosophical rituals. The other two such officials
appear in Star Trek: The Motion Picture & Star Trek III: The Search for Spock, are different characters, & are played by different actresses.
T’Pau, the priestess officiating at Spock’s wedding in “Amok Time” is played by Celia Lovsky, the former wife of Peter Lorre. T’Pau
(played by two different actresses) also appeared in one episode of Star Trek: Voyager & three episodes of Star Trek: Enterprise.