Tzim-Sha’s re-emergence in the finale would tie together a season that’s felt largely episodic and disconnected so far, helpings things come full circle in as only Who can.
As previously mentioned, Tzim-Sha’s Stenza race is one of the only species that has been mentioned more than once within the season.
That next mention came in “The Ghost Monument” when it was revealed the Stenza were behind the “cleansing” of a character’s planet which resulted in a mass execution.