Siblings Abroad is Chapter 7 of Fire Emblem: The Blazing Blade.
Passing through Kathelet, Lyn and co. encounter Nils, a traveling bard, who begs Lyn to rescue his sister, Ninian, from some thugs. At first, Kent objects, but when Lyn says she wants to help Nils, he gladly decides to help. Before the battle begins, Lucius, an Elimine monk, appears from a nearby inn and offers his assistance.
Subjective: The following part of this article is subjective to the editor's writing. Therefore, it may not work for everyone.
In order to unlock the Gaiden Chapter, you need to beat Heintz in 15 turns or less, so you want to get to him as quickly as possible. The fastest way is to have Florina carry Lucius over the mountains to the south. Once you are over, release him.
There are only 3 enemies (not including Heintz) that could possibly give you trouble, the 2 Shamans and the Brigand. Lucius and Florina, despite their low HP, have a lot of resistance. The Shamans should give them no trouble at all. The brigand is a bigger problem, but if both Lucius and Florina gang up on him, you can probably kill him in one turn.
Once the area is free of enemies, heal if needed, then have Lucius engage Heintz. He is only slightly stronger than the other Shamans, so you should not have a problem with him. (If you really want the Pure Water from the Northeast village, you should send a high mobility unit like Kent or Sain to get it).
- Heintz (Boss): Shaman L5 w/ Flux
- 2 Brigands L1 w/ Iron Axe
- 2 Mercenaries L1 w/ Iron Sword
- 1 Archer L1 w/ Iron Bow
- 1 Brigand L2 w/ Iron Axe, Iron Lance*
- 3 Shamans L1 w/ Flux
- 1 Mage L1 w/ Fire
*Dropped when defeated
- Northeast: Pure Water