Abandoned Knight had Steam trading card support added on 7 May 2016. There are 5 cards in the series, and you'll receive 3 cards at random for purchasing and playing the game.
Trading Cards
Foil Cards
Badges
Booster Pack
Emoticons
Profile Backgrounds
Crystal
(common)
(common)
Nightmare
(common)
(common)
Pest
(uncommon)
(uncommon)
Cyclops
(uncommon)
(uncommon)
Abandoned Knight
(rare)
(rare)