In this AU, Cadance has the role that Tempest Shadow had.  
 
A pegasus that lost one of her wings when she was young, trying to save her friends. She grew lonely and bitter, eventually falling prey to King Sombra, the former tyrant that ruled the empire before being dethroned and locked away by Shimmer and Shadow.  
 
She aided in the invasion of the city and stole the crystal heart for him. However, she soon realized that Starlight was right about him not actually caring about her, as he immediately tried to kill her for “outliving her usefulness”. Starlight got in front of the blast, showing Cadance what true selflessness is.  
 
Cadance would help Starlight heal and her friends get the heart back and destroying Sombra for good. At the celebration, she revealed to Sonata that her real name was “Mi Amore Cadenza” which Sonata said was “The most beautiful name she had ever heard ever”.