How to Enter Old Scholomance - Farm Once-Removed Transmog Items

wowhead.com:

Scholomance was one of the instances originally lost to time, receiving a revamp in Mists of Pandaria. The revamp has led to several transmogs and recipes being lost to time and becoming unobtainable. However, in Patch 10.1.5, you're now able to regain access to the old instance! We went through all the steps to unlock it in this post.

Thanks to the Secret Finding Discord for locating all the steps! The first step to unlocking old Scholomance is to have someone in your group with the Krastinov's Bag of Horrors toy, obtained from Doctor Theolen Krastinov, a rare spawn in the new Scholomance. You do not need to have the toy yourself, but you must have someone with you who has the toy in order to start the secret. To start unlocking old Scholomance, you must first do a normal run of the MoP-Revamped Scholomance all the way to the final boss, Darkmaster Gandling. Once you complete the run, you must go to the room that used to be Doctor Theolen Krastinov's room in the original Scholomance (top center room), and at the top left portion of the room, you will be able to loot the first item of the secret, Eva's Femur.

At this point, you must use the Krastinov's Bag of Horrors toy on top of the location where you looted Eva's Femur. When you do, the ghost of Eva Sarkhoff will spawn, afraid of you (as the toy transforms you into the Butcher himself). Removing the toy's buff will make Eva realize you're not her murderer, and she will talk to you, giving you the old Spectral Essence trinket.

This allows you to see ghosts in Caer Darrow. Once you do, you can talk to Eva at her old spot outside Scholomance, where she will request you to look for her journal, as well as five candles, to perform a horrible ritual. The candles are