Fire Emblem: Shadow Dragon Tips

Easy 2-turn finish on Endgame (Last Chapter)
If you don't feel up to killing everyone in the last map, here is how you can finish the game in two go.

First, you only need few units. Bare minimum, you need two units that can use staffs. For me, it's Elice and Lena. I also brought along Beck and that's all I used. Equip one of your two staff-wielding units with Barrier and the other, Warp. And both, Fortify. It would help if Beck have Thunderbolts packed as well. No need for a Door Key.

Equip Marth with Falchion. Most important thing is Marth needs to be as strong as he can be. Meaning, level 30. Now place all units in that locked room with Marth. If you only brought two staff-wielding units and Beck, they should all fit there.

First turn, use Barrier on Marth. Then Warp him into the room with Medeus, preferably at the staircase at the upper left corner. Once there, go and kill that Sniper in front of you. Use Beck and a thunderbolt to hit that Ballista in front of the room. Finish him off with Gotoh and Swarm. This ensures none of your units get killed in the room.

Your turn ends. The enemy will move the Manakete in front of Medeus to attack Marth. The counterstrike should kill him easily if Marth is at max-level. The Sniper on the other side will attack as well, as well as a Ballista at the far left and a Bishop with Swarm on the right. And if you get hit by all attacks, it's alright. No more units can attack after that and Marth has at least 50-something HP by then, he can take them.

Your turn again. Let's finish this. Use both Fortify. Then move Marth to fight Medeus. For me, he killed Medusa in one battle, I deal 34 damage x2 and he deals 24 damage once. As long as Marth don't miss and not get critical hit by anyone, that should be the end of Medeus.

And all it took is 2 turns. =)