31 cards where the colors is U and the text includes “destroy”

Acid Rain (Masters Edition IV #36)
Aether Storm (Masters Edition II #39)
Blue Elemental Blast (Masters 25 #43)
Dwindle (Core Set 2019 #53)
Erosion (Fourth Edition #70)
Ethersworn Adjudicator (March of the Machine Commander #222)
Flash Flood (Masters Edition III #35)
Frozen Solid (Coldsnap #35)
Giant Albatross (Homelands #27a)
Hakim, Loreweaver (Mirage #68)
Hydroblast (Eternal Masters #55)
Ice Cage (Magic 2012 #57)
Knight of the Mists (Visions #36)
Merfolk Assassin (Time Spiral Timeshifted #25)
Musician (Masters Edition II #56)
Ovinomancer (Dominaria Remastered #64)
Polymorph (Magic 2010 #67)
Pongify (Outlaws of Thunder Junction Commander #106)
Possessed Aven (Torment #45)
Psychic Allergy (The Dark #34)
Rapid Hybridization (Ravnica: Clue Edition #93)
Siren's Call (Fourth Edition #101)
Stormscape Battlemage (Commander 2013 #58)
Teferi's Response (Invasion #78)
The Phasing of Zhalfir (Dominaria United #59)
Threadbind Clique // Rip the Seams (Wilds of Eldraine #239)
Tolarian Emissary (Invasion #81)
Viscerid Drone (Masters Edition II #73)
Vodalian War Machine (Fallen Empires #32)
Volcanic Eruption (Fourth Edition #112)
Winter's Chill (Ice Age #107)

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