BS Fire Emblem
Boah served as an advisor to the King of Archanea prior to the war with Medeus. When Grustian army lays siege to the Archanean Palace, the king orders Boah to escort Princess Nyna to safety. Boah arranges for Midia, captain of the guard to escort Nyna out of the palace, however General Gubel blocks their escape. The Archanean knights are able to defeat Gubel, however they are soon stopped by General Camus. Camus is quickly smitten by Nyna, and spares their lives, however he has Boah and the knights sent to dungeon, separated from Nyna.
In Shadow Dragon, Boah and the knights had outlived their usefulness as prisoners, so General Volzhin has them prepared for execution. When all seems lost, Prince Marth frees Boah and his companions from prison, and capture the palace. As Boah travels in Marth's army, he ponders about who Nyna should marry, and narrows the selection down to Marth and Prince Hardin.
Mystery of the Emblem
After the war with Medeus is finished, Boah has Nyna marry Hardin to boost the morale of the Archanean people. Despite knowing that Nyna is in love with Camus, he forbids Nyna from speaking of him, and doesn't tell Hardin about Camus. Eventually Hardin discovers this deception and is greatly depressed by the situation. Gharnef posses as a merchant selling magical artifacts, and uses the Darksphere to brainwash the mentally weakened Hardin. Hardin turns into a brutal tyrant and declares war against all the other nations of Archanea, and gives Nyna to Gharnef. Boah tries to stop Hardin, but is mortally wounded in the process. He meets up with Marth and tells him about the tragedy of Nyna and Hardin, begging for Marth to save the princess, and to forgive his foolishness.