Inspired by Flashlight237 comments on the magic suppression ring that, "might give Twilight a hard time if something goes wrong."
So that prompted some thought on a 'emergency escape system' to remove the ring sans magic. Which then lead to redesigning the sarcophagus introduced in part II. This cutaway view artwork illustrates two things to solve the issue Flashlight237 pointed out.
1. Originally the magic suppression was just on a string tied to an eyelet. Here it's hooked on a chain to a spring loaded pulley. It works like pull down blinds. One good pull and the system pulls off the ring, and Twilight can use magic to escape from her self made captivity.
2. Originally the lid of sarcophagus was loose and put in place with telekinetic unicorn magic. Here not only is the lid is hinged on one side, said hinges are also spring loaded. The lid will always stay open until it is swung close and locked. Locks that will automatically release the lid when the pulley system for the ring is engaged. Thus opening the lid and also freeing Twilight from her self made captivity.