In what a Knight of Hope would serve Hope to his team-mates? By encouragements? Speaking of Knights, what powers would a Knight of Void have?

Encouragement, ‘never give up’ sort of personality, and maybe literally empowering buffs with Hope Majyyks, who knows. As for the Knight of Void, wielding the power of the Void is certainly a scary concept. Either Horrorterrors or just, the ability to Serve Nonexistence, can be pretty obliterating.