169 cards found matching energy cost is 3

Jagged Cutlass
Janna
Jinx
Karthus
Kayle
Kennen
Kinkou Initiate
Kog'Maw
Kraken Hunter
Last Breath
Last Rites
Last Stand
Laurent Bladekeeper
Lecturing Yordle
Legion Quartermaster
Loyal Poro
Loyal Pup
Lucian
Lunar Boon
Marching Orders
Mask Mother
Mirror Image
Mistfall
Moonfall