Dandelion is Chapter 12x of Fire Emblem: Thracia 776.
This chapter can be very easy depending on how you go at it. The easy way is using a torch to light the immediate area, and warping Lara next to Pirn (with Safy and the Warp staff if she has a high enough staff rank) to recruit him and have Lara promote to a dancer. After Pirn is recruited, every enemy, excluding Tina, will attempt to flee the map. If you want to recruit Trewd, warp another unit close to the second exit from the left to prevent him from fleeing the map quickly. Have another unit block the exit to the stairs to keep Trewd from fleeing that way and then Pirn will get the chance to talk to him because of Pirn's movement Stars. At this point, the treasures can be easily accessed and Tina can be easily recruited.
However, if you cannot use the warp staff, there as an alternate, albeit harder, method. If you want to recruit Trewd you can put him to sleep (with Salem) and then capture him, or weaken him with a magic attack and then capture him with a strong character. You may have to part with some treasures due to the distance. Lara can get some of the treasures you pass, but you will need to capture the thiefs who steal treasure chests in the western part of the map. The enemies should not be much of a problem as they only have slim swords.