Fight against the fourth boss: Killer Ape. Fight starts at 0:48.
No Djinn are used in battle for extra challenge.
Party & Djinn Setup
Mia - Setting Mars Djinn on Mia in this mod does not remove ply from her psynergy list, making it a great class for healing and offensive spells. The downside is the very low Agility, which I made up for by equipping Mia the nerfed Elven shirt, boosting her agility by 15, instead of multiplying it by x1.5.
Ivan - Decided against granting healing psynergies to Garet or Isaac, therefore I set Mercury Djinn on Ivan. With the highest agility in the party, Ivan heals with items when required. Ivan is still the main psynergy damage dealer.
Isaac - Between Venus and Jupiter, Jupiter is a better option as it switches Isaac's healing psynergy for support psynergy. In this mod, he gains the extremely useful psynergy Paralyze. Not very useful against bosses, however.
Garet - Venus Djinn Garet for higher attack. Garet becomes the main phsyical damage dealer.
Golden Sun Reloaded is a mod for Golden Sun and Golden Sun: The Lost Age, created by Caledor from the Golden Sun Hacking Community.
More info on the mod can be found here: http://forum.goldensunhacking.net/index.php?topic=2779.0