The other main character of Fire Emblem: Awakening beside Chrom. The Avatar is Chrom's right-hand man/woman and the tactician of the Shepherds.
The Avatar is called My Unit in the Japanese version, just like the similarly player-created character of the Japan-only Fire Emblem: Shin Monshou no Nazo - Hikari to Kage no Eiyuu. The Avatar's default name for both genders is Robin (Rufure in the Japanese version).
In initial character creation, the player can choose the Avatar's gender (male/female), build (child/young adult/adult), face, hair, hair color, and voice. For voice, the player can alternatively choose a silent protagonist option, where the Avatar communicates with other characters in very vague ways (ellipses, question marks, and exclamation marks), though this option is absent in the English version of the game.
On the second page of character creation, the player can enter the Avatar's name, birthday (month and day), "asset" (strongest stat), and "flaw" (weakest stat).
At the beginning of the game, the Avatar has a dream in which he and Chrom work together and defeat the evil Validar, but their victory is short-lived when a desperate attack by Validar causes the Avatar to lose control of himself and kill Chrom.
When he awakens, the Avatar is found in an open field by Chrom, Lissa, and Frederick. Having lost his memory, he can remember nothing save his own name, as well as Chrom's. Though this arouses Frederick's suspicion, the Avatar travels with the group, and during a battle with bandits, realizes that he actually has a great deal of tactical knowledge. After being introduced to Chrom and Lissa's sister Emmeryn, the Exalt of Ylisse, he joins the Ylissian militia known as the Shepherds as their tactician.
Over the course of the game, the Avatar and Chrom come to trust each other implicitly, though both are aware that something isn't right as the Avatar suffers from occasional strange headaches, as well as hearing an odd voice in his head. Two years after the game's start, he and Chrom visit a rebuilding Plegia and discover to their surprise that Validar, whom they had previously killed when he attempted to assassinate Emmeryn, has become king. Adding to their surprise, in Validar's company is a figure that looks exactly like the Avatar.
It is ultimately revealed that the Avatar was born with the intent of his becoming the vessel required for the revival of the fell dragon, Grima. However, as a baby, he had been spirited away by his mother, who took pity on him. When Lucina and the other children traveled back in time in order to prevent the oncoming destruction, the Avatar's future self did so as well. The future Avatar had intended to merge with his counterpart in the past, ensuring that Grima's revival would come to pass, but the past Avatar was too weak, and as a result the merging failed and the Avatar lost his memory. But even as Chrom and the Avatar worked to change their future, the future Avatar manages to revive Grima on his own.
After Chrom performs the Awakening ritual with Naga to unlock the full power of the Exalted Falchion, Naga informs the Shepherds that there are two possible ways to stop the fell dragon. If Chrom slays Grima with the Falchion, Grima will be put back to sleep, but will inevitably reawaken one day to threaten the world again. On the other hand, if Grima were to be slayed by his own blood (that is, the Avatar), he would actually be killed and never threaten the world again. However, in doing so, the Avatar would also perish, and would only have even the slightest chance of surviving if he shared strong enough bonds with others to keep him from departing the world.
To end the game, the player must slay Grima with either Chrom wielding the Exalted Falchion, or with the Avatar wielding any weapon. If the Avatar finishes the fight and kills Grima, he will vanish, but everyone remains hopeful that he's still out there somewhere. After the credits roll, a short epilogue plays that mirror's the game's opening, with Chrom and Lissa once again finding him asleep in a field. Chrom helps him to his feet and welcomes him back.
Although not by name, the Avatar functions similarly to a Lord character; if they die, it is an automatic Game Over.
The Avatar begins the game as a Tactician, able to wield tomes and swords, and through the use of a Master Seal, can promote to Grand Master. They are the only character that can change to any class through the use of a Second Seal.
The Avatar is the only character who can romance every other opposite gender character, including second-generation characters. Their child from the future is either a son or daughter named Morgan whose gender is the opposite of the Avatar's. Morgan can have a sibling depending on who the Avatar marries, or can be an only child.
Lyn suggests that the Avatar may be the Tactician from Fire Emblem and asks if he/she remembers their adventures with her. They can either say yes or no.