I remember that Derpy or Rainbow didn't save Twilight in time before she was hit by ones of those crystallizing balls by Tempest Shadow herself and was turn to stone.

She and the other princesses magic was taken by the Storm King and he ruled Equestria for years.

The alicorns princesses stones was place somewhere with the other leaders from different kingdoms who would turn into stone as well but still somehow was able to talk to each other though mind link.

Tempest Shadow herself was feeling guilty about what she done and turned herself into stone alongside with the others.

That's all I can remember.

Really appreciated if someone find it for me so I can read again thank you