Eva is Princess Ava's evil twin sister and the main antagonist of the series. She is one of the two kittens of the fictional Felis Aulicus breed ("Cat of the Royal Court" in Latin), the rarest in all the world.
Jealous of Ava's position of power, she hatches a plan to steal the Friendship Heart while her sister is busy with the Friendship Ceremony. She ends up breaking the Friendship Heart in two and accidentally sending Ava to the Big City. She escapes capture with one half of the jewel, leaving the other half in the heroes' paws.
Determined to become the next Princess of Pocketille, she does everything she can to recover that half and keep Kate, Magic, and the Royal Guards from bringing Ava back. As fate would have it, however, this dark obsession leads to her end as the Petbuster's prisoner.
Eva is brave, smart, and good at hiding her true feelings, considering Ava never knew how much she hated her until Eva told her. She's also excellent at deciphering others' weaknesses, as she did with the snow leopard guarding the Never Alone flower. Durillia refers to her as the most cunning creature in all of Pocket Kingdom.