Morva is a Manakete that serves as the leader of the Manaketes of the Darkling Woods. He was once the leader of the Five Heroes who managed to defeat and seal the Demon King Fomortiis 800 years before the events of Fire Emblem: The Sacred Stones. He is also Myrrh's foster father.
Morva was known as the "Great Dragon" and was recognized as the leader of the Manakete tribe in the Darkling Woods for what can be assumed to be multiple centuries. 800 years ago he was the leader and sixth member of the Five Heroes who defeated and sealed the Demon King. He went uncredited in history, which is why the legends speak of the Five Heroes despite him being the sixth member of the group.
Since the defeat of Fomortiis, Morva watched over his lifeless body to prevent his return and protect humanity. It is during this period that he adopted a young Manakete girl by the name of Myrrh and started to watch over the human village of Caer Pelyn. While his daughter was away to investigate the great evil she had detected in Grado, Morva confronts Lyon when the latter tries to gain entry to the Black Temple. In Eirika's route he meets the fully possessed Lyon, vowing to kill him, while in Ephraim's route he tries to dissuade Lyon, before realizing that he was being possessed by Fomortiis himself.
He fails to stop Lyon who kills him and turn him into a Draco Zombie and left under Riev's control. When he dies, Myrrh gets a sudden feeling of sadness, feeling her father's death. If Myrrh confronts him, they will get a short exchange where she appologize to him before finishing him off.