Daybreaker:…Oh i got a idea and is a win-win!  
Celestia: ?!  
Daybreaker: You be in control most the time but where is time to battle, I take control, I promise to not hurt our pony’s!  
Celestia:…..Are you try to fool me?  
Daybreaker: Nope! Think of it, I know you fear of one, Twilight and her freinds will fail and you want be powerful to protect them, Yes we need our subject to can fight on their own but not every evil can be reform or seal away, You know the danger of other space, those alien invader, You know, is by Force we need to take them away, Yes some will come in peace but some will come to destroy us, and trust I will not wait to see everything we are work so hard take way by them, think of it, you dont need to tell yet, in you , you know is the right thing to do, plus be in harmony with ME!  
Celestia:……………….You are right but dont lie and dont betray me, got it!  
Daybreaker: Hey, I am not like Nightmare moon, she use luna, not like me! I wait for over 1000 years to learn of you so i know when i can win and when i dont, we will stronger, Of course we need to learn how to work together and we can to all is possible to be in perfectly in harmony with your own dark self and be save to summon them!  
Celestia:……….Fine but We will help Luna to Control Nightmare moon!  
Daybreaker: Yeah but she will be a challenge! you know how Nightmare moon think, right partner?  
Celestia: Yes but we need to talk to Twilight of this, we never know if thing go wrong!  
Daybreaker: Well with her, is will be trouble!  
Celestia: But why you want to work with me? the last time i see you, You are try to destroy Nightmare moon!  
Daybreaker: Oh this? well you see, i lose control of my self by the tantabus and make act as true evil i can be, sorry to show my dark side like this!  
Celestia:….is logic, Luna a create this thing to hurt her self by turn her to nightmare moon and to make remenber to never be like this and one day she lose control of it,is true my dream control is not be perfect!  
Daybreaker: This is why we need to be all together, Twilight need to control her own dark form!  
Celestia: She dont have one and the same for Cadance and flurry heart!  
Daybreaker: Flurry is too young for have one, But Twilight and Cadance have one, I dont know the name of the one inside Cadance but i do know the one inside Twilight, MIDNIGHT SPARKLE!  
Celestia: Midnight sparkle?! are saying the Midnight sparkle of the dimension where Sunset live is the dark form of Twilight?!  
Daybreaker: Of course! OH, we will continue this a other day, you have guest!  
Celestia: !?(she wake up from her meditasion) Oh Twilight!?  
Twilight: Hello Princess!

@G.S.
 
C: “You may be a part of me, but you don’t control me!”
 
D: “Heh…we’ll see about that.”

“You can’t hold me back forever. One day, I will get out.”

@Background Pony #0762
 
@Nightweaver20xx  
Yes. This needs to happen!

@Background Pony #0762  
Now there’s a fanfic I don’t want to see.

From the thumbnail, I got the impression that Celestia’s head is growing out of Daybreaker’s butt.