Aversa's background and true objectives are unknown, but her dark clothing and magic book makes her appear to be a user of ancient magic. She seems to be as cruel as Gangrel. Her Shadowgift skill allows her to use Dark Magic, despite not being a Dark Mage or Sorcerer. Her birthday is November 3rd. She bathes longer than anyone else in the army and is the fondest of taking long swims.
Aversa is first introduced when Gangrel kidnaps Maribelle. After failing to negotiate to seize the Fire Emblem from Emmeryn she attempts to murder Maribelle until Ricken manages to repel her with an Elwind spell and she leaves the battlefield. Later during Emmeryn's assassination, when the Ylissean Pegasus Knight squad lead by Phila is about to rescue her, Aversa summons a group of Risen Archers and kills the Pegasus Knights.
Two years after Gangrel's downfall, Aversa becomes the subordinate for the new king of Plegia, Validar. Aversa talks to Excellus at some point during the conquest of Valm, offering to give him the Plegian throne if he managed to get the Fire Emblem from Chrom. Aversa used Excellus as a medium to take Valm down from the inside should Chrom's army fail to take down Walhart.
After defeating Walhart's forces Chrom is summoned to Plegia Castle to give him the final jewel for the Fire Emblem, however this was a lie and Validar seizes the Emblem from Chrom by controlling the Avatar. Validar leaves to go to The Dragon's Table to awaken Grima. Aversa stands out of the temple to give Validar some time to perform the ceremony. She summons the Deadlords to stall them as long as possible, but she is ultimately defeated. However Validar is given enough time to perform the ritual, and Aversa flees for the time being. After Validar's death and the resurrection of Grima, Aversa stands before Chrom one last time at Origin Peak to kill Chrom's army for revenge from killing Validar. However Aversa is apparently killed by Chrom and the Avatar, leaving them to face Grima.
In her Paralogue, Aversa has survived her last stand and has arrived at the Wellspring of Truth seeking answers. She encounters Chrom and the Avatar who recently caught wind of the legendary spring. Aversa invites them to fight with her on the map to learn about their own truths. If Aversa survives the map, Aversa will remember horrible events of her past. She was once a young, innocent village girl who lived a normal life. However, one day Validar came to her village out of sheer chance and noticed her talents. He kidnapped and brainwashed her into doing his bidding, changing her name to Aversa somewhere down the line. To make sure that no one could possibly undo her brainwashing, Validar slaughtered everyone who had prior connections with Aversa, including her parents. Horrified that she once served her parent's murderer she vows to take down Grima. Chrom invites her to join his cause which Aversa accepts, seeing this as an opportunity to atone for her past actions.
After the war, Aversa returns to her hometown where she lived her life as a normal woman possibly to make up the lost time taken away by Validar.
In her supports with the male Avatar, she feels that no one in the army truly trusts her and lives away from camp. Despite this the Avatar tries to warm up to her only for her to coldly dismiss him. Nevertheless Aversa enjoys teasing the Avatar, calling him "Big Brother" much to his discomfort. In the end though, she opens up to him and decides to join in with everyone so she won't feel lonely. This can go further if they S-Support, feeling that only the Avatar gives her hope, Aversa wants to marry the Avatar, which he accepts. In Aversa's supports with the female Avatar, the two become overly competitive against each other to try and see who the better tactician for Chrom is. Aversa reveals that she is eight years older than Chrom. By the end of the support, they decide to duel each other to see who is more fit to serve Chrom, but after they are ambushed by enemy soldiers, they realize that it would be better if they combined their talents instead of fighting each other.