Now, other than Dullahan himself, the Golden Sun games are pretty easy as far as RPG's go. As long as you can work out a decent strategy and aren't afraid to use whatever resources you have at your disposal, you're going to win 99% of the time. Even in the dungeon where Dullahan is the boss nothing's really going to cause you too much pain or effort. Without grinding too much or even at all, by the time you reach the game's real end boss (the Doom Dragon), your parties would be at the high 40's-low 50's range in terms of levels. And at that point, nothing can really even touch you other than the Doom Dragon itself. Dullahan, however, is not only a super hard secret boss, he's a boss that was specifically designed to piss players right off. For one, if you plan on taking on Dullahan without summon rushing him, you absolutely NEED to have every character at at least level 60 or higher to even have a chance. Otherwise he WILL destroy both of your parties in 6 turns or less. Why is this? Well let's see here:
Dullahan's primary attack, the one he uses most often during the fight, will always hit, does pretty hefty damage, and has something like a 10-25% chance to insta-kill whomever he hits with it. Dick move #1
He has attacks called Djinn Blast(?) and Djinn Storm, one of which basically reverts one character to their base stats and the other reverting every character on the field to their base stats. Usually with some careful playing this is something you can survive, but due to how the Dullahan fight works this may as well be a death sentence. Dick move #2
Dullahan attacks 3 times per each of his turns, and at the end of each of his turns he automatically regains 200 HP and 30 PP. In other words, you need to do a minimum of over 200 damage to even phase him, and he's not running out of his scary magic attacks any time soon. Dick move #3
If at any time Dullahan decides that you've taken away just a little too much health, he will suck a fair chunk of HP out of two of your party members and take it for himself, on top of the 200 HP regen at the end of his turn. Dick move #4
Dullahan, at a certain point in the fight, can summon Charon (the second most powerful summon in the entire game) whenever he damn well feels like it, and you better believe he's going to summon it a LOT, sometimes summoning it 3 times in a row, which may as well be a death sentence for your party if he decides to do so. Dick move #5
So yes, Dullahan is specifically programmed to piss you off and kick your ass, and should you decide to fight him the "proper way", that's probably what he's going to do. Is he unbeatable? Of course not. With some decent on-the-fly strategies and maybe a bit more level grinding, he can be beaten. Due to the batshit crazy amount of health he has, however, that fight is going to take a damn long time, and that's assuming he doesn't just say "Djinn Storm, Charon, Charon", which is entirely possible. So, the developers have gone and made a boss that can really only be reliably defeated by using what some people consider a cheap tactic: the Summon Rush, where you go in with all your Djinn on stand-by and just unleash all of your summons on him, praying to whatever gods you believe in that he decides to fall over before he kills all of your party members again. If he uses Djinn Storm, well you're boned. Reset the game and try again. If he doesn't, then you'll more than likely take him down.
