Arcana Knight Joker can only be special summoned by using King's Knight, Queen's Knight and Jack's Knight as Fusion Materials. (You cannot use fusion substitute monsters.) But after being this difficult to summon, he comes with excellent stats and a protection effect which makes him somewhat worth the effort. You can negate any effect that targets him by discarding a card of the same type.
Arcana Knight Joker can only negate effects that target him and only if you have the same type of card in your hand, so your boss monster might be in danger under some situations. To save him, you can use Interdimensional Matter Transporter to temporarily remove him from play.
King's Knight and Queen's Knight's combo puts all three Knight monsters in your field making this card usable, Helps you recover Arcana Knight Joker and draw a card if ever he is sent to the graveyard.