The answer is standing right in front you (Patreon)

 Gold Scryer trotted down the palace hallway in my Equestria dreamscape but her mind was far away in a different place. She'd just left from a meeting with both Princess Celestia and Luna where she was able to report a little progress in her investigation on the origin of the mystery wards that had been used in the break-in of Celestia's office. Whispers from the past. 

  
  It was not much but the mage was of the opinion that they were dealing with one of three possible scenarios: 

 1. The mysterious mirror ponies were not a creation of some ponies imagination, and so how they had remained hidden in Equestria culture for more than thousands without being detected, or they had returned and were now attempting to accomplish some unknown agenda. 

 2. Some pony, or ponies, had by some means had discovered some source or sources of information that was allowing them to recreate the magic of the mirror ponies. 

 3. A mage or group of mages working in secret had developed a new branch of magic, and the fact that it was similar to the ancient formula in the book was accidental. A case of convergent development. 

  
  She'd hoped that perhaps that name mirror ponies might have been something that Royal Sisters had heard during their early days of Equestria. Alas, neither Celestia or Luna could provide any additional knowledge. Although they both agreed that they would send inquiries to every university, library, and government archive in the realm seeing if somepony might be able to shed more light on the mystery. Also they agreed to assign additional staff to Gold Scryer's team of researchers. 

  
  Celestia also said that she had several of her operatives working in the field tracing the origin of the wards used by Rakorno back to their original source through several criminal organizations. Progress was slow and it had also uncovered several criminal enterprises that had not come to the attention of the Royal Court.   

  Still Gold Scryer felt she hadn't made enough progress and that time was running out. Under oath of secrecy she'd been informed of what Rakorno had apparently attempted to steal. This meant she only had a few months to solve this before the wedding of Shining Armor and Cadence. Still so many questions to answer.  

 
  Corporal Trotter was living up to his name today. He trotted down the hall at brisk pace as he ran an errand for the watch officer of the day. Although his meeting with his new handler Purple Marten had gone late into the night; at the end of it he felt that they'd made some meaningful progress. A Plan Takes Form 

  
  Purple Marten was proving to be very knowledgeable about running an operation of this complexity, and she'd been able to help him resolve a couple nagging issues in his initial concept.   
  So it was that two individuals, not really focused on where they were going almost collided in the hall.  

 
  Fortunately they didn't actually collide but they did find themselves both abruptly coming to a halt in the hall. What followed was the usual volleys of apologies. 

  
  "Oh! Excuse m'am!" Exclaimed the corporal. "Sorry. I wasn't paying  attention to where I was going like I should've!"

 
  "No, no. It's all right I wasn't watching where I was going either." Said elder mage. "I've got a lot on my mind!" 

  "I know the feeling." Said the disguised changeling rhetorically. "I'm dealing with a mountain of problem myself!"

 
  "Got any good ideas for tackling an insurmountable mountains?" Asked the Gold Scryer with a tired chuckle in her voice. 

  "Well for what it's worth m'am sometimes it helps to think of a mountain in terms of the individual rocks that make it up. Sure there may be lots of them but they're usually smaller in size and easier for a pony to wrap their mind around them."  

 
  "And if that doesn't work try stepping back and don't look at the mountain at all. Do something else for awhile then tackle getting to the summit from a different direction." 

  Suddenly a thought popped into Gold Scryer's mind. She'd been searching through numerous prim and proper unicorn treatises, grimoires, and great tomes of magic, but the entry in the tattered journal had talked about the mirror ponies as possibly being the source of many tales and legends amongst the earth pony settlement. Knowledge that was rarely of any interest to pre-unification unicorns of the court, who had looked down upon the earth ponies with a disdain.  

 
  But maybe she might be able to get some better ideas and direction by seeking out  the works and chronicles of earth pony folklorist. She knew of a couple at Canterlot University who might of assistance. 

  "Well it's a long shot but it couldn't hurt trying." Said the mare out loud. "Thank you corporal...." 

  "Trotter is my name m'am. See! Sometimes when you step back you discover the answer is standing right in front of you! Now if you'll forgive me; I do have an errand I must complete. Good day!" 

  Then Gold Scryer and Corporal Trotter went their separate ways. 

  
 To be continued.