Fire Emblem: The Sacred Stones Codes -

Bonus characters:
Complete the indicated task in the listed chapter to unlock the corresponding character.

Amelia: In Chapter 9 of Ephraim's storyline, have Eirika or Franz talk to her on Turn 5.
Colm: In Chapter 3 of Eirika's storyline, have Neimi talk to him on Turn 2.
Comrag: In Chapter 13 of Eirika's storyline, have Eirika talk to him. In Chapter 10 of of Ephraim's storyline, have Duessel talk to him.
Dozla: In Chapter 11 of Ephraim's storyline, have L'Arachel talk to him.
Ewan: In Chapter 12 of Ephraim's storyline, visit the small house on Turn 5.
Garcia: In Chapter 2 of Eirika's storyline, have Ross talk to him.
Gerrick: In Chapter 10 of Eirika's storyline, have Innes talk to him.
Innes: In Chapter 10 of Eirika's storyline, have Tana or Eirika talk to him.
Joshua: In Chapter 5 of Eirika's storyline, have Natasha talk to him.
L'Archel: In Chapter 11 of Ephraim's storyline, have Ephraim or Eirika talk to her.
Lute: In Chapter 4 ofEirika's storyline, visit the lower-left house.
Marisa: In Chapter 10 of Eirika's storyline, have Gerik talk to her. In Chapter 12 of Ephraim's storyline, have Ewan talk to her
Rennac: In Chapter 14 of Eirika's storyline, have Eirika or L'Arachel talk to him.
Ross: In Chapter 2 of Eirika's storyline, have Eirika talk to him.
Tethys: In Chapter 10 of Eirika's storyline, have Gerik talk to her.

Another way to get Comrag in Chapter 10 of Ephraim's storyline is to have Tana talk to him. It is difficult due to the ships. Just have Comrag come north after he decides to leave his post.

The following characters are only available in Extra Mode. Successfully complete the game to unlock the Ex. Map in Extra Mode. Play that map and complete the indicated area. The corresponding bonus character will join your party during the next battle.

Riev (Bishop): Complete the Tower, 7F.
Fado (General): Complete the Ruins.
Glen (Dragon Master): Complete the Ruins, round 5.
Hayden (Forest Knight): Complete the Ruins, round 5.
Ismaire (Sword Master): Complete the Tower.
Caellach (Hero): Complete the Tower, 3F.
Lyon (Necromancer): Complete the Ruins three times.
Orson (Paladin): Complete the Tower, 6F.
Selena (Mage Knight): Complete the Tower three times.
Valter (Wyvern Knight): Finish the Ruins, round 7.

See support conversations:
Successfully complete the game, then select the "Extras" option. You can choose to see all of the support conversations that have been unlocked.

Super Trainee class:
Successfully complete the game in Eirika's Ephraim's storylines. Play the game a third time, and Ross, Amelia, and Ewan will have the option to be promoted into the "Super Trainee" class.