The Laws of Sacae (サカの掟, lit. Law of Sacae) is Chapter 18B of Fire Emblem: The Binding Blade if you take the Sacaen route (which happens if by the end of Chapter 16, the experience points gained by Sue and Sin were more than or equal to that of Shanna and Thea).
Inside the houses in this chapter, the villagers all just talk about the 'Law of Sacae'. The houses surrounding the gate cannot be visited, but rather serve as potential spawns for reinforcements. On every turn player units are left inside the area enclosed by the houses 0-4 Nomads/Nomadic Troopers will spawn from random houses surrounding the gate. These reinforcements will spawn even after Monke is killed, and will spawn for around 18-20 turns on Hard Mode.
4 enemies in this chapter carry Elixirs, one of them being Monke and 3 carry vulneraries
- After the area enclosed by the houses is entered, for every turn player units are left in the area 0-4 nomads/nomadic troopers will spawn from random surrounding houses. They continue to spawn every turn for as many as 20 turns on Hard Mode or significantly less on Normal Mode (I'm not sure if the amounf of turns is random or not, especially since 0 can spawn and you can't be sure if thats still a spawning turn or not). Note that these reinforcements will continue to spawn even after Monke is killed.
- Turn 10: 2 Nomads and 1 Nomadic Trooper from southwest
- Turn 12: 2 Nomads and 1 Nomadic Trooper from southeast
- Turn 13: 3 Dragon Knights from northeast
- Turn 15: 2 Nomads and 1 Nomadic Trooper from southwest
- Turn 17: 2 Nomads and 1 Nomadic Trooper from southeast
- Turn 20: 2 Nomads and 1 Nomadic Trooper from southwest
- Turn 22: 2 Nomads and 1 Nomadic Trooper from southeast
- Turn 23: 3 Dragon Knights from northeast