Train your lords in arenas (smart) or in combat (not very smart) to the combined level of 50 before the level "Four Fanged Offense" and then you will access an alternative "Four Fanged Offense" level where you are in Bern and you do not get Wallace. Instead, a level 3 Warrior appears to the bottom right of the screen named Geitz. If you talk to him with Dart then he will become yours.

In Lyn's Quest, train Nils to at least level 10 (this can be done by making a character wait every turn and than letting Nils Play for them. After beating Lyn's Quest, begin Eliwood or Hector's Quest. when you get to the level "The Dread Isle", beat it in under 20 turns to be asked to embark on a side quest. Accept this and you will enter the level "Prisoner of Magic". After a few turns in this level a Magic Seal unit called Kishiuna will appear. Kill the boss, than surround Kishiuna. If you kill him, than you will be asked to embark on another side quest called "A Glimpse in Time".