|Men and Monsters|
“Having won the day and put Camus and his Sable Order to rout, Marth and the League moved on to the mountains in eastern Grust, to crush the last of the opposition. The surviving Grustian soldiers, in a mad attempt to hang on to their lives, took all the residents of a nearby village hostage to keep Marth from striking. However, they could not have picked a worse village to harass...”
Men and Monsters (The Lair of Fire in the North American version) is Chapter 20x of Fire Emblem: Shadow Dragon.
To advance to this chapter, complete Chapter 20: Camus the Sable with 15 or fewer units alive. Ymir will appear at the beginning of the player's turn at the upper right corner and can be recruited by talking to him with Marth, then he will leave the map. After that, seize and he will be available next chapter. In the chests you can find: a Wo Dao, a Longbow, a Poleaxe, a Killer Bow, a Killer Lance and a Killer Axe. Also, be sure to bring a thief in this chapter to open the chests, or you can give Marth the fire emblem. The boss should not be too hard to defeat, despite being a general.
Talk to Ymir with Marth and he will leave, when you complete the chapter, Ymir will join your army. Do not forget to get all of the treasure chests in this chapter. Get all of the treasure and fight Larissa. The next Gaiden Chapter is Chapter 24x, so have Tiki die and have no Falchion.