Instant effect
Decrease Buff Duration
Decrease Buff Duration is the game's own name for this effect on the battle screen. The game gives no separate description for it.
Champions with it
50 champions have a skill with a Decrease Buff Duration effect, according to the effect lines in the game data. This lists who has it and on which skill, not how strong it is or how often it happens: values and chances are on each champion's page.
Achak the Wendarin Devour All Hope
Aeshma Languish
Alice the Wanderer Vorpal Sword
Andryssia Pointed Justice
Arbiter Enforced Humility (all enemies)
Bambus Fourleaf Grovetender (all enemies)
Bladechorister Caldor Orchestra of War (all enemies)
Carlinia Burn With Shame [P]
Chalco the Blind Unrelenting Violence
Flesh-Tearer Lay Low
Gaellut, Son of the Pact Beheading Strike
Galleus Bloodcrest Sonic Torture
Genbo the Dishonored Heartless Blitz
Gharol Bloodmaul Kill or Cure [P]
Gizmak the Terrible Magma Hurl
Godseeker Aniri Quest For Meaning (all enemies)
Guardian Chop
Harvest Jack Leering Grin [P]
Hierophant Lazarius Nest of Vipers (all enemies)
Highmother Maud Anointed Phalanx
Holguk of the Hallowsights Hallowhex
Hope Holy Storm
Inquisitor Shamael Unnamed skill; Wreak Revenge
Iron Brago Molten Pummeling
Justiciar Comeback [P]
Karilon the Ringer Deathknell
Keeyra the Watcher Smashing Spree
Lady Mikage Silkensnare
Lord Entertainer Fabian Spectral Flourish (all enemies)
Lugan the Steadfast Mark of Silence
Malkith Bloodflock Hemobomb
Marius the Gallant Death or Glory
Nobel Smell Fear
Norog Maul
Pontiff Augustin Your Eminence [P]
Sandlashed Survivor Endless Sands
Sanguinia Red Punishment
Searsha the Charred Conflagrate
Shemnath Caryatid's Curse
Sigmund the Highshield Equitable [P]
Skeletor Havoc Scythe
Skeuramis Effortless Superiority (all enemies)
Spider Calamity
Spymaster Spymaster's Blade
Strategos Islin Hindrance (all enemies)
Talenna Soulseer Quell The Darkness
Thenasil Wither
Timit the Fool Test Your Strength (all enemies)
Vanguard Dismay the Foe [P]
Vott Head-lopper Righteous Killing
Taken from the game data and not tested in battle here. See Data quality.