18 cards where the illustration contains “flute”

Bag of Holding (Adventures in the Forgotten Realms #240)
Bone Flute (The Dark #97)
Citanul Flute (Tenth Edition #315)
Citanul Flute (Urza's Saga #289)
Composer of Spring (Commander Masters #739)
Ecstatic Piper (Defeat a God #3)
Farseek (The Lost Caverns of Ixalan Commander #242)
Firbolg Flutist (Commander Legends: Battle for Baldur's Gate #174)
Gnawing Crescendo (Wilds of Eldraine #131)
Jukai Naturalist (Kamigawa: Neon Dynasty #225)
Merry Bards (Wilds of Eldraine #140)
Midsummer Revel (Urza's Saga #268)
Musician (Ice Age #85)
Pestilence (Fifth Edition #186)
Song of Totentanz (Wilds of Eldraine #353)
The Second Doctor (Doctor Who #156)
Totentanz, Swarm Piper (Wilds of Eldraine #216)
True Polymorph (Adventures in the Forgotten Realms #80)

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