Just when Garon seems defeated, he becomes something more powerful. Kill him to end the war once and for all.
Defeat the Boss
You start the battle in the center of the map. Enemies will come toward you throughout the battle, so you will want to move your units to an edge of the map to avoid being surrounded. Be warned that the Sigil tiles around the edges of the map will spawn enemies throughout the battle.
Garon can use the nearby Dragon Veins to turn different areas into Blight tiles, healing himself in the process. Your units will be damaged if they are standing on blight tiles at the end of the turn. Because of this, you will want to end the battle as soon as you can.
In spite of Garon's dragon appearance, Wyrmslayers don't work well against him. Just have Corrin attack Garon with the Blazing Yato, and if any of your other units can do damage to him, use them as well. Once you finally bring Garon's HP down to zero, you win the game. Congratulations! After the credits, when it says The End, press A and you will be prompted to turn five of your units into Einherjar units, which you can purchase from the Einherjar Shop in your castle (if you build it), allowing you to use those units in battle.