18 cards where the set is “vow” and the cards are in the Innistrad: Crimson Vow Dracula Series

Circle of Confinement (Innistrad: Crimson Vow #329)
Savior of Ollenbock (Innistrad: Crimson Vow #330)
Thalia, Guardian of Thraben (Innistrad: Crimson Vow #331)
Jacob Hauken, Inspector // Hauken's Insight (Innistrad: Crimson Vow #332)
Jacob Hauken, Inspector // Hauken's Insight (Innistrad: Crimson Vow #332)
Thirst for Discovery (Innistrad: Crimson Vow #333)
Falkenrath Forebear (Innistrad: Crimson Vow #334)
Henrika Domnathi // Henrika, Infernal Seer (Innistrad: Crimson Vow #335)
Henrika Domnathi // Henrika, Infernal Seer (Innistrad: Crimson Vow #335)
Innocent Traveler // Malicious Invader (Innistrad: Crimson Vow #336)
Innocent Traveler // Malicious Invader (Innistrad: Crimson Vow #336)
Sorin the Mirthless (Innistrad: Crimson Vow #337)
Voldaren Bloodcaster // Bloodbat Summoner (Innistrad: Crimson Vow #338)
Voldaren Bloodcaster // Bloodbat Summoner (Innistrad: Crimson Vow #338)
Vampires' Vengeance (Innistrad: Crimson Vow #339)
Reclusive Taxidermist (Innistrad: Crimson Vow #340)
Edgar, Charmed Groom // Edgar Markov's Coffin (Innistrad: Crimson Vow #341)
Edgar, Charmed Groom // Edgar Markov's Coffin (Innistrad: Crimson Vow #341)
Eruth, Tormented Prophet (Innistrad: Crimson Vow #342)
Olivia, Crimson Bride (Innistrad: Crimson Vow #343)
Torens, Fist of the Angels (Innistrad: Crimson Vow #344)
Investigator's Journal (Innistrad: Crimson Vow #345)
Voldaren Estate (Innistrad: Crimson Vow #403)

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