A moon near Vulcan, once home to an ancient civilisation, where an encounter with the non-corporeal Kerkhovians left Spock temporarily fully human in the episode Charades.
Kerkhov is a moon in the Vulcan system surveyed by the USS Enterprise in the Strange New Worlds episode Charades. Its builders vanished long ago, and scans pick up an odd energy reading above the surface.
Spock and Christine Chapel take a shuttle to study it and collide with what turns out to be a passage into another dimension. The Kerkhovians, luminous beings without bodies, repair the two travellers before sending them back, but with only Chapel as a pattern they remake Spock as entirely human.
The timing is awkward, since he is about to host a ritual dinner for T'Pring's parents. While he struggles with unfamiliar emotions, Chapel, Uhura and Ortegas fly back into the anomaly. The Kerkhovians behave like bored clerks until Chapel admits how much Spock matters to her, and they provide the means to restore him.