1. First, if I open the mirror just as I get out of the door, "Fated Persuasion" seems to not be upgraded, though it is. Also, it has 1000 D cost.  2. The cost goes to 0 D after reopening the mirror (with the provided button) 3. Using this mirror to upgrade something can break it, as it can be upgraded past it's max. I managed to upgrade Stygian Soul to -12 sec. 4. After switching to "Fated Persuasion" I keep the 8 re-rolls: 
First, if I open the mirror just as I get out of the door, "Fated Persuasion" seems to not be upgraded, though it is. Also, it has 1000 D cost.
The cost goes to 0 D after reopening the mirror (with the provided button)
Using this mirror to upgrade something can break it, as it can be upgraded past it's max. I managed to upgrade Stygian Soul to -12 sec.
After switching to "Fated Persuasion" I keep the 8 re-rolls:
