mitsu

Ok... You acn get inside, but you need all the djinnis from both games... When you meet up with Isaac and crew, they will be holding some of the djinnis from golden sun 1, but not all of them... They will only be holding all of them if you played golden sun 1, found all the djinni in that game, and transferred your gamedata to golden sun 2 with either 2 gameboys and a gamelink cable, or by entering the gold code you can get form the golden sun 1 game. If you didn't do this... Then you will never be able to get all of the djinni... Even in golden sun 2. Because to get at least one of the djinni in golden sun 2, you need to have gotten a special item in golden sun 1 called the 'orb of force'... But only if you got it and transferred data... Otherwise isaac wont be holding it when you meet them again. If you havent met up with isaac and crew yet, you may be able to find a gold code online... That will give you these items and all the djinni. But the code is Lo-oo-ng...

Yes. It will definitely open when you get all of the djinnis... And inside, there are items, forgeable items, and the hardest battle in the game. Seriously. It's incredibly difficult. If you win, you will receive an incredible summon synergy that does a huge amount of damage! It's a great place to level up your party, too.