Melia is one of the most important characters to join Shulk's party This is due to her being the first offensive mage of the game, providing a new way of defeating enemies and another ranged attacker other than Sharla.
Melia is the Daugther of the current emperor of Alcamoth. She has an Elder brother who's name is Sorean. She is the second in line to inherit the throne of the City, and looks more like a hom than a High Entheletia. The reason behind this is due to a breeding program past emperors started in order to ensure the race survived if Zanza was ever freed from his prision on top of the Bionis Head.
 Meeting Shulk and her Ascension to the Throne
She meets Shulk soon after the first time the party faces an telethia attack, she is found unconscious soon after and is grateful for being rescued, she introduces herself and joins the party, also she refuses to accept that shulk live Alvis can see the future, it is not until the second time they are attacked by a Telethia that she believes him, soon after she scorts them onto the city and after the group is arrested she is the one to appeal in their favor, she aslo ends inviting them to her Villa.
During the events of Alcamoth we learn that not everybody is happy. She is a heir to the throne and while she is performing her personal test the party learns that there is a set up inside the Catacombs to kill her, ensuring that her older brother takes the throne (since the political situation hints heavily that she will be the one inheriting the seat from her father) since Shulk and company are successful in stopping the assasination attempt. The forefathers tell her that she is indeed worthy of inheriting the throne (this is also because she is 80% hom and 20% high entheletia since she is one of the few immune to Zanza's wave of transformation).
Later on she is separated from Shulk. After some events inside the Mechonis, she ends up joining with Sharla and Ryen and eventually finds shulk. After the game is finished, she is seen helping to rebuild the city and is now the ruling empress of Alcamoth.