It looks like you just removed him from the formation. Since you can only have 10 Crusaders in the World's Wake formation, you do need to choose which of the twenty you will use. You can click and hold on a Crusader's portrait and drag them onto the field.
 "Clicker Heroes"){kind=icon}
 "Crusaders of the Lost Idols"){kind=icon}
 "Swords and Souls"){kind=icon}
 "Bloons TD 5"){kind=icon}
It looks like you just removed him from the formation. Since you can only have 10 Crusaders in the World's Wake formation, you do need to choose which of the twenty you will use. You can click and hold on a Crusader's portrait and drag them onto the field.