Rainbow Dash has no experience in dealing with doctrines nor demons. In fact, she doesn't have any knowledge of their existence. When she is thrust head first into a steadily building catastrophe, she will have to put her life on hold in an attempt to do her civic duty.
Discord, however, has a history with these creatures, being almost as ancient as them, but after three and a half thousand years encased in stone, he is feeling a little stiff. He also doesn't want to be stiffed, knowing that one of the ponies who incarcerated him in the first place will not release him lightly; not without an ace in her mane. Especially not Luna, she disliked him especially.
Luna knows a great deal of the past: Centuries of research and innumerous amounts of time spent delving into magics that no unicorn could hope to perform has allowed her that luxury.
The princess realises that those who do not learn from the past are destined to repeat it. She also wonders which of her companions will be the most difficult to control. The only thing she knows for certain is that her sister cannot catch wind of the situation arising, nor of her plans to suppress it.
If Celestia found out, Equestria would never survive.
***
"It has been theorised that this great land once had another ruler, one that shaped and molded it into the place we now know. One far older than our fair princesses and those who came before them, one that breathed our ancestors to life. Of course, no amount of theological discussion can lead to any concrete evidence, and the teleological debates regarding the extrinsic value of our own land and technology is inconclusive also. Epistomologically, we must assume that there is no greater power than the entities which we are aware of, until it is shown otherwise."
Swirl, Star. The Extrinsic Elements of Metaphysics: A Compendium of Theory and Conjecture. Canterlot, Royal Canterlot Library, 2988 ND. 3rd edition.
