Previous Versions can be found here.
Knight Knight is a strong card to deploy near the end of a game. Though it has a rather hefty price tag with a lower attack, this card can restore HP to itself equal to the DMG it dealt to a target (effects like Armor affect it). It doesn't need to kill the target to heal up.
There are 2 major things to keep in mind. Firstly, this effect doesn't work while defending. Secondly, if its HP goes <= 0 before it heals up, it dies anyway.