You've said that there's a SLIGHT chance of dust joining forces with the player if, there is a greater threat that both need to overcome to save the timeline. The player obviously doesn't want the timeline to be destroyed and dust just wants the player gone, not the whole timeline itself... So hypothetically, if they were to call a temporary truce... What would their relationship be like? And I'm guessing it doesn't take much for him to betray this weak truce anytime... Lots of back stabbing I'm guessing...
Example:
Player: looking forward to working with you! *Holds hand out to shake*
Dust: likewise =)
*twists their arm while shaking it, crushing their plan in hand*
Player: ;-; ow...
As you said, an appointment in the two will be a kind that can be broken at any time. Sometimes the human break first, sometimes he breaks first. They can betray or promise by deceit from the beginning. They only intend to deceive and use each other.












