Modern players rejoiced when this card was revealed. It has three abilities that are all relevant in the format. Here are a couple of decks that will gladly accept Knight of Autumn into their lists.
Knight of Autumn can be played in different variants of Collected Company decks that utilize both white and green colors. It will find its rightful place amongst such cards like Knight of the Reliquary and Gavony Township.
Knight Exemplar and Aether Vial make up a fantastic Knight tribal deck, to which Knight of Autumn would be a perfect addition. The deck has to be played in a rather aggressive manner using such enchantments like History of Benalia and Rancor.