Golden Sun/Venus Lighthouse Aerie

After dropping down the hole, an elevator will carry the party to the aerie of Venus Lighthouse. Here you'll overhear Saturos and Menardi arguing with Felix and Sheba. Eventually you'll enter battle with Saturos and Menardi.

First Battle
Defeating Menardi first would be recommended as she has the the Death Size ability that not only is dquite damaging but also could potentially instant-down one of your allies. Also, she has less HP (at 2600) than Saturos (at 3000).

Saturos will be the one doing most of the damage and other status effects. He will also cancel status buffs, so increases won't do much.

You can utilize using multi-attack Psynegy or Mercury-based summons in this battle to make haste on this battle. Keep in mind recovery time for the next battle

If you have the Gaia Blade, now is a good time to have Isaac spam attacks.

Defeat them and another cutscene will follow. The Venus beacon is lit, Felix and Sheba leave, and Saturos and Menardi merge to form the Fusion Dragon, attacking the party.

Doom Dragon
Despite being just 1 monster, Doom Dragon will have 2 attacks. Fusion Dragon has a very devastating attack, called Outer Space, which behaves similar to Meteor summon. Feel free to unleash all of your summons in battle, heal up to the max, and win.

Epilogue
Once the dragon is defeated, another cutscene leaves Isaac and friends back in Lalivero. They resolve to seek out Jenna and find Lemuria, and receive the Black Orb needed to pilot Babi's ship. Enter the guarded building in the northwest corner of Lalivero town and walk to the end of the gangway. Use the Black Orb to access the Lemurian Ship.

To Be Continued in Golden Sun: The Lost Age. The Lost Age manual will tell you how to get the passcode from this game to The Lost Age for transfer.