Fire Emblem: Shadow Dragon/Chapter 23

Dark Pontifex "With the aid of the White Sage Gotoh's powerful Warp magic, Marth and company were transported to the faraway city of Thabes. Once, Thabes was an advanced civilization; but only its decay advanced now. The League traced the lifeless streets to the temple at the city's heart, somewhere within its walls Gharnef was waiting, and now, Marth must wrest Falchion and his sister, Elice, from the fiend's grip."

Preparation
Before the battle, give the Iota Shield to one of your fliers (ie. Shiida). Then, give Starlight to one of your mages (ie. Merric).

Just move forward the first round, and dialogue will appear.

Begin
You probably got attacked by an archer and a mage (with Swarm) last round. Just eliminate the archer and heal whoever got attacked.

The goal on this map is to kill the three Gharnefs first, then to take care of the boss. The first guy to kill is the Gharnef to the bottom. It might take a few turns because of the healers using physic and fortify, but Starlight will kill him. On turn 7, IF Gharnef is still alive, he will summon in some more enemies.

Now, the best way to approach the nest above is to use Beck to eliminate the mages and healers first. Some of them will charge, and use Swarm to do damage. Others are just normal mages, but nevertheless, don't risk sending units forward to attack since there is at least one mage at the top who can pick you off with Swarm. Once they reach the staircase, it is OKAY to send other units to clear the mages.

By the time you clear the first wave of mages, Gharnef will cower out again (if he is dead already, then you will not see the reinforcements) and decide to send yet another wave of reinforcements in. Do the same to them as you did the first wave.

After the second wave, Gharnef stops sending more mage reinforcements. Now is the time to move your units in. Lure in the Swarm mage to attack Beck, then destroy him. Move the rest of your units in and kill the healers and other enemies.

Before you attack the second Gharnef, make sure to destroy all other distractions. Then, send in whoever has Starlight to kill the Gharnef.

The real Gharnef when attacked will say: "Heh heh heh... You dare challenge me, fool?? You must not value your life. Cower before the might of the dark magic Imhullu!"

Gharnef should be no problem if you have a decent mage using Starlight. The healer to the left is annoying, and he will prolong the life of Gharnef. But no matter, Gharnef will fall after a few turns (use your own mage to support your mage)

When he dies, the dialogue is as follows: "Agh! What... Where did you get... Starlight...? Still, you are a fool... Your power is not enough to defeat Medeus... I shall be waiting in the pits of the inferno... for when he sends you to join me... Heh heh, ha ha ha!"

(Obtain Falchion)

There is still one Gharnef left. However, feel free to put in a chapter save since the most part of this chapter is over. Send in your mage again to defeat Gharnef, but first use Beck to kill the healer there.

The boss isn't anything special. Kill him with a weaker unit for great exp. He also drops a Master Seal. Before seizing the gate, be sure to grab the chests way back where you spawned.

Seize the gate.