13 cards where the text includes “spirit” and the set is “stx”

Blood Age General (Strixhaven: School of Mages #93)
Hofri Ghostforge (Strixhaven: School of Mages #192)
Illuminate History (Strixhaven: School of Mages #108)
Illustrious Historian (Strixhaven: School of Mages #109)
Lorehold Apprentice (Strixhaven: School of Mages #198)
Lorehold Command (Strixhaven: School of Mages #199)
Lorehold Excavation (Strixhaven: School of Mages #200)
Make Your Mark (Strixhaven: School of Mages #204)
Mascot Exhibition (Strixhaven: School of Mages #5)
Quintorius, Field Historian (Strixhaven: School of Mages #220)
Reduce to Memory (Strixhaven: School of Mages #25)
Returned Pastcaller (Strixhaven: School of Mages #224)
Spirit Summoning (Strixhaven: School of Mages #236)

The message was clear to Sorin—time to search for something else.