Validar is a major antagonist of Fire Emblem: Awakening. He first appears in the game's prologue; a dream in which Chrom and the Avatar face him in what is apparently their final battle. Validar is struck down, but before he can be killed, he uses magic to take control of the Avatar, who kills Chrom.
When first properly introduced, Validar is a member of the Plegian court and a vassal of King Gangrel. He is sent on a mission to assassinate Emmeryn, the exalt of Ylisse and Chrom's older sister, but the plan fails due to the interference of Lucina, and he is supposedly killed. However, he is brought back from death by a mysterious figure that claims to be Grima, the fell dragon.
Two years after the war between Ylisse and Plegia ends with Gangrel's death, Validar reemerges as the new king of Plegia, flanked by Aversa and a figure that looks exactly like Chrom's friend, the Avatar. He provides Ylisse and Regna Ferox financial aid in the war against Walhart of Valm, but stops short of providing soldiers, claiming that the Plegian army is still too weak following their loss in the previous war. Chrom and the Avatar, however, both suspect something is wrong the moment they see Validar, as they both saw him killed during the attempt on Emmeryn's life.
It is eventually revealed that Validar is the leader of the Grimleal, a secret cult that strives for the revival of Grima. He was saved from death by Grima himself, who in the human guise of the Avatar traveled back in time to prevent Lucina's own plans from altering the future. The Avatar was actually born with the purpose of serving as Grima's vessel for revival, but vanished when the Avatar's mother betrayed the cult and stole the baby away to safety.
Validar manages to take the Fire Emblem, necessary for the ritual to revive Grima, by controlling the Avatar, who is forced to steal it off of Chrom's person in order to deliver it. In the battle to reclaim the Fire Emblem, Chrom and the Avatar face Validar, just as events had played out in the dream at the beginning of the game. However, the Avatar had recognized that the dream was a premonition, and through complex trickery, manages to foil Validar by faking Chrom's fatal injury. They also reveal that they had fooled Validar from the start; when the Avatar handed him the Fire Emblem, the five gems set into the shield were fakes, meaning that Validar never had the full Fire Emblem at all.
His every plan thwarted, Validar dies on the field of battle, leaving Grima to awaken his dragon form himself.