16 cards where the text includes “spell or ability an opponent controls causes you to discard”

Ajani's Last Stand (Core Set 2019 #4)
Dodecapod (Dominaria Remastered #220)
Guerrilla Tactics (Tenth Edition #211)
Loxodon Smiter (Return to Ravnica #178)
Mangara's Blessing (Mirage #25)
Metrognome (Urza's Saga #301)
Nephalia Academy (Eldritch Moon #205)
Nullhide Ferox (Guilds of Ravnica #138)
Obstinate Baloth (The Brothers' War #187)
Orvar, the All-Form (Kaldheim #70)
Psychic Purge (Masters Edition #45)
Pure Intentions (Saviors of Kamigawa #25)
Quagnoth (Future Sight #150)
Sand Golem (Mirage #318)
Spiritual Focus (Mercadian Masques #49)
Wilt-Leaf Liege (Double Masters 2022 #294)

This search is finished. Now the real work can begin.