Twilight Sparkle had designated Rainbow Dash to fly all around Equestria to search for Nightmare Moon. Knowing Fluttershy would be too scared to go on her own, Twilight sent Fluttershy with Rainbow to assist her. During their search, Rainbow and Fluttershy had herd disembodied laughter. Searching frantically for its source, Fluttershy had noticed Rainbow's Element of Harmony slowly disappear, as if it was sinking into her neck. She immediately told Rainbow Dash who suspected Discord to be behind it, and began searching the immediate area for the draconaquus.

Several hours later, Rainbow unexpectedly lost control and crash landed on a nearby cloud. Fluttershy had flown over to investigate, but couldn't find her anywhere. She reported the incident to Princesses Celestia and Luna. They had told Fluttershy to stay in Canterlot, because they knew Fluttershy was too fearful to go alone, and they had no idea where any of her friends were.

Once she was sure Fluttershy couldn't hear her, Celestia told a royal guard to order the LTF Foundation to go on a search and rescue. After several days of searching Ponyville, field crews had decided to try the Everfree Forest. Foundation personnel eventually found an area in the Everfree where the trees had mostly fallen. A mucus-like substance found on their barks was presumed to be the cause. It was also rainbow-coloured, which suggested Rainbow Dash was connected to this. Rainbow Dash was later found attacking a foundation employee. Before back up could reach the employee, both he and Rainbow had disappeared. The next day, his body was found in the Everfree. It was mostly corroded by the same rainbow-coloured mucus found on the trees in that area.

Weeks later, after several attempts at containing Rainbow Dash, Dr. Jack Bright had produced a theory on Rainbow's abilities. After seeing her pass through trees and spread the mucus onto them in one attempt, he theorized that Rainbow possessed the ability to pass through solid matter. He also theorized that when she disappears with people, she takes them to what was called a "Pocket Dimension" where she would then hunt and kill her victims, discarding their body back into Equestria. The corroded body from the first incident further supported his theory that she would kill them in her Pocket Dimension, before getting rid of their remains. Dr. Bright also gave an idea on how to contain her. This was to provide a "lure subject", break his/her stifle (horses thy), and lift a containment unit via a mag-lev system once Rainbow had appeared. Field crews were immediately successful at containing her.