Rarity, knowing very well whom his other parents are (As in my AU I have retconned her relationship with AJ and Rainbow and instead she ends up with Sombra during attempts to reform him), still treated Atropa as her precious little gem, lavishing him with toys, gifts, and attentions. This generosity, however, created a unicorn whom feels near entitled to the same devotion and attention from everyone else around him. Being ignored or not given his way tends to flare up the sore temper he inherited from his father Sombra.