My version of Dust loves to compete, no matter how much he says it's pointless and a great waste of personal time. He's hypocritical in a way, he says to not like competing, yet always ends up competing with someone to prove he's right and they're wrong - and that's the second thing about him — he LOVES being right and hates admitting on being wrong, too stubborn to say it. Horror knows it, he oh so knows how much Dust loves to compete, and he doesn't mind giving it to him, poorly because it brings Dust some joy in being right (he doesn't realise it that he does it solely to see Dust happy, and even if he was aware of this personal factor of his, he would rather die than admit it). He competes with him by making up stuff about something Dust is knowledgeable in, or in anything else that might get Dust to compete with him. And Horror makes it easy for Dust to get competitive and act impulsively, despite Dust having an immense amount of patience and self restrain (something Horror might lack in). They bring out traits of each other that they won't let out in front of others, Horror bringing out Dust's impulsive and competitive behaviour, and Dust bringing out Horror's patience and self restrain. They bring out the opposite of each other, something they particularly 'lack' (Dust 'lacking' impulse and competitiveness due to his "eye of patience and determination', and Horror lacking patience and self restrain due to loosing his 'eye of patience and justice')