Clear the room of Heartless and strike the door, synthesizing to make 1 or more. Go to the north door in Room 2 and synthesize to make 2 or more. Keep getting rid of all the Heartless in Room 3 and head to the door to the right. Strike it and synthesize to make 3 or more. Now you'll be in Room 4. Repeat, except this time you'll have to synthesize to make 4 or more. In Room 5, after killing all of the Heartless, use an Attack Card with a value of 3 or more and the Key of Beginnings. Here you battle Genie Jafar.
This boss fight, once again, is much the same as the one in Sora's Story, which you should be seeing here all too often. The Soul Eater, like the Keyblade, won't do any direct damage given to Jafar. Your attacks will amount to nothing on his HP bar. Obviously, this means you have to look for either a new strategy or a new target. In this case, it's a new target. Iago will be flying around aimlessly with Jafar's lamp. It would probably have been much smarter of him to fly around behind Jafar, but that's besides the point. He's supposedly flying out of your reach. This is until Jafar brings down his fist and the platforms rise and fall. Simply jump on the risen platform and Iago should be in your reach. Attack away and Genie Jafar's HP will drop. You'll have to avoid Genie Jafar's attacks while you do this though, and these attacks include:
- Jafar picks up a large, molten boulder and throws it at Riku. Card break this one, as jumping probably won't avoid the huge thing.
- Jafar brings his fist down and the platforms rise and fall. If you're giving Iago some combos in mid-air, this shouldn't affect you.
- Jafar sends a blast of energy Riku's way. This can be avoided by going behind a risen platform or card breaking.
Once you've defeated Genie Jafar and get the card as well as the EXP, go back to Room 3 and strike the remaining door. Synthesize to make 3 or more. Clear the room of Heartless, go through the door, and you'll end up back at Castle Oblivion.