These notes were made to the Mushroom walkthrough listed in the line below. Download it and apply these notes to that. It was kind of big so I didn't want to put it all here.
Kingdom Hearts II: Final Mix XIII Mushrooms FAQ By DarkHelmet543
The Mushrooms are tough. I played these guys on Critical Mode at level 99, with STR and DEF maxed out. On some of these, stats make no difference at all, but on others, they do. The ones where strength matters were defeated fairly easily under these conditions, and I have no experience with playing them at lower levels. Some of the notes in this FAQ are arguably misleading to me so I’m going to add what I learned as I went through it.
I wouldn’t worry about what he says about the ‘finisher’, just use a decent keyblade and don’t worry about your Abilities. Using Fenrir and setting up like he suggests made it harder for me. Luck is your best bet for winning this one since things happen really fast. Approach the Mushroom, go into Wisdom Form then press triangle to activate it. Press triangle twice to ‘confuse’ the Mushroom. Press ‘O’ nine times (three sets of three), then press triangle twice again (immediately, don’t wait for any reaction). Repeat this process until done. Problem is, the Mushroom may double cross you and reverse your reverse and you will be hit. If this happens even once, you don’t have enough time to win. You can wait a fraction of a second after pressing triangle twice to see if the Mushroom will react by reversing to be in front of you, if it does, you can press triangle again to re-reverse. Problem is, if this goes on for long you will run out of time anyway, even if you don’t make any mistakes. Bottom line, you need luck. The Mushroom will occasionally not double cross you on any of your reverses and you will win. That’s why waiting to see if the Mushroom reverses your reverse is probably a waste of time, just barge on and hope it doesn’t because eventually it won’t.
Like it says below, but I like to back up to near the edge before I jump up and hang, just to help keep the Mushroom in sight better.
Glide is faster than Wisdom Form, but it’s much easier following the mushroom around in Wisdom Form. It seems Wisdom Form absorbs orbs better than Glide too. If you use Glide, sometimes it’s good to drop down and land where the orbs are coming to the ground to gather more of them. This one is tough.
Yeah, like it says below. After you go into Wisdom Form, approach the mushroom and press triangle to start the battle, be ready to quickly back away or you’ll be hit immediately.
At level 99, this is one of the easiest Mushrooms. If you do what it says in the paragraph below, there’s a good chance you’ll beat him on your first try. Go into Final Form, press Triangle, jump and start pressing ‘O’ like mad. I don’t have any input for fighting at a lower level.
The strategy below is a good one.
I don’t understand the part about the jumping, but I guess it doesn’t hurt. Target the mushroom and try and stay in contact with it. You’ll be thrown back when it attacks and if you get too far away, the Reflega won’t be able to reach anything to reflect.
I like the ‘alternate method’ described at the end. Like it says, you can only win if you get lucky, but it shouldn’t take too many tries until you do win.
The instructions below will *not* work. You do need to use Wisdom form and Thundaga, but as far as I can tell, only the first Wisdom Shot will make the Mushroom spin. From then on you have to occasionally use a Thundaga to keep the Mushroom spinning (after about each 10 hits, use another Thundaga). It’s not the number of spins that count, but the number of hits the Mushroom takes while spinning.
When you activate the Mushroom, immediately back up toward the entrance of the cave where the treasure is then turn back and hit pause. You need to back away because the target mushroom will often fly out of view if you don’t. Once you orient yourself, press Start and begin the Start/Pause sequence until the mushroom gets in line. Be sure to close on him soon as you know where he is going to land and be sure the target icon is on him before you attack.
Easy in concept, but hard to make it in time. The second part about Fatal Crest doesn’t make any sense to me, it sure doesn’t seem to be faster. First, approach the Mushroom, go into Wisdom Form, then target. Now activate the Mushroom and don’t stop pressing ‘O’ for any reason (I put the controller on the desktop so I can press the button like a telegraph key for more speed). If you get good luck and the Mushroom takes plenty of hits, you’ll beat it, otherwise, you’ll just have to do it again (maybe many times). I don’t know anything you can do to ensure you’ll win.
Again, many of the instructions below will *not* work and don’t be fooled, this is a tough Mushroom, not easy at all. Do it like this. Approach the mushroom to get the triangle prompt, but don’t activate it. In the Main Menu, select Drive, then go down to Wisdom Form but *don’t* activate it now either. Press Triangle and three mushrooms will quickly appear in front of you. Soon as they do, then go into Wisdom Form. The transition into Wisdom Form will instantly kill all three mushrooms. If you don’t do it this way, at least one of the three will just about always escape, and you sure don’t want that. Immediately move toward the gate and Mushrooms will begin to appear there. You need to target and shoot quickly. Don’t shoot more than twice at any single Mushroom unless you absolutely have to. When a Mushroom is targeted, shoot immediately. Don’t wait for the Mushroom to be hit, soon as the Wisdom Shot leaves the Kyeblade, quickly target the next mushroom and shoot right when the blue target icon appears. After you get about 30 kills, some Mushrooms will spawn up high over pillars or off to the side. You have to back away from these for the shots to be able to reach them. You’ll probably need many tries before you get familiar with the flow of this little battle, but with experience, it does get much easier.