Part I. First Lesson
When we crossed the door, we ended up at (what?) Traverse Town.
When I said, "Huh?! We're in Traverse Town?!" Pink Ranger and his (yes, his) partner appeared, saying, "Not necessarily. This is merely constructed from both of your memories."
As I pondered on what they said, Jiminy suddenly came out saying that we're "five heads short". When we turned around, we saw that only Sora and I are the ones who managed to make it through.
"What have you done to them?", Sora asked.
"They are at the mercy of the cards now." In rage, I attempted to cast Petrify on the two of them, but at the next second, I realized that I no longer had my "Materia Bracelets" and when I rummaged at my bag, I saw the "Materia Chest" was locked.
Pink Ranger then said, "Heheh. As I had crossed over you, I locked that chest so you would not be able to use your abilities and to put you down to the same 'level' Sora is currently at. But worry not; we will teach you how things in this castle go. The key to the chest is with me." and suddenly, we were in a 'battle matrix'.
"The rules of this castle bid your friends turn into cards. If you value them so much, you will obtain them without fail.", they said and at that moment, 2 green cards of Donald and Yoris respectively bounced around the field.
As we ran to them, they were automatically collected. (I was somehow able to see my HP and my current 'deck' using a heads-up display in my helmet and when I focus on someone else, let's say Sora, I was able to see his HP and 'deck' too on the right portion of the display since mine is on the left) As we automatically used our cards, Donald and Yoris appeared from a white portal (the same way our summons did), casted fire attacks on the hooded figure and the Pink Ranger, then disappeared again (Donald and Yoris, not our 'instructors'). They then instructed us to try attacking us and as we did, I saw that each act used up a card.
They then told us "Everything in this castle is ruled by cards. Whether an enemy or a door stands in your way, cards are the only way to proceed. But you mustn't forget your own strength."
We discovered that our 'own strength' were our jumps, Sora's Dodge Roll, and my Defend (with my shield, of course, which was suddenly transformed from a grey riot shield into a blue medieval-style shield). They then instructed us to use up all our cards, and once we did, I saw that my current card was now a black one with a number.
"There. You have no more cards, and without them, no power. If you want that power back, you must focus. Bid the cards to return to you, and they will."
When we did what they said, the blank card (which was actually the reload bar) filled up and when it was filled, our used cards (except for the green ones, which we find out to be Friend Cards) returned (Guess I no longer need to worry about charging the DirLuxGun for now, I thought).
"The strength of your heart brought back the lost cards. You can recall spent cards any time – you only need to wish it. But each time you do, the cards will take longer to return. The cards are by no means unlimited. Use them wisely. Anticipate the flow of battle and choose the most effective cards. You may use any card in your deck."
After we practiced on 'switching' between cards, they then said "The four card types you can use in battle are grouped into two wider categories. The first category includes attack cards, magic cards, and item cards. The second category consists entirely of enemy cards. To use a card from a different category...", I forgot what followed but I did obey what they said.
As we accessed the "Enemy Cards", they then finished the lesson by saying, "Cards will empower you whether you are attacking or defending. But it is up to you to decide when to attack and when to defend. Do not forget it."
After the tutorial (my heads-up display disappeared), our friends were back and when I asked what had happened to them they said that when they crossed the door, they were engulfed by a white light and that's it, whereas Sora and I managed to enter 'Traverse Town'. Just then our 'instructors' told us to master the cards and make our way through the castle. However, only Sora and I are permitted to travel while our friends are in the form of cards. While our friends protested, I knew there was no changing the rules of the castle and I promised them Sora and I would stick together and help one another.
"Hmm, the hero speaks so boldly. Go, then. The rest of Castle Oblivion awaits. Walk the avenues of latent memory, and you shall meet someone dear to you.", our 'instructors' said and they vanished.
Jiminy then came out saying that he's got a bad feeling about this and I said, "We'll be ready for any tricks, Jiminy. Besides, how hard is it to figure out the cards?"
Everyone else then disappeared and we were on our own. We then approached the door and I realized only Sora can open the doors by hitting it with his keyblade (shooting at it only made a bruise in it) Just before the door opens, we were in a small matrix which consisted of us standing in front of the door and 'Map Cards' around us. We also saw a hollow card with a criteria request, and when I saw or only cards so far (a blue 'Moment's Reprieve', and a Keycard named 'Key of Beginnings') Sora used the blue card and we crossed it.
We were then at a sector of 'Traverse Town' though it seemed weird and resembled a 'room'. We then saw a 'Save Point' ahead and once we 'saved' we saw a Shadow appear, when I shot at it, the 'battle matrix' initiated (I knew since my heads-up display reappeared) and more Heartless appeared. We took care of them easy and collected the EXP that have dropped and also a red card named 'Tranquil Darkness'.
After collecting everything, the 'battle matrix' dissipated (and my display disappeared too). We then saw another door ahead and crossed it (after using our newly obtained red card). As we found Heartless all over the place we battled them each time. We also saw barrels which we busted and Sora got more attack cards (for now, this is the Kingdom Key.) We also obtained other cards too, HP balls, 'Moogle Points'. (I could only put non-attack cards in my deck, which are magic, items, and enemy cards. After applying those cards, then my attack cards appear at random values, which are named DirLuxGun, and fill up my 'CP' to full. Of course, I can't put in any of Sora's attack cards since I'm CAN'T hold the Keyblade even temporarily; he needs it to use his attacks and magic).
Eventually, we found a door which required the Key of Beginnings (and a couple more cards too). As Sora used up Map Cards (under my supervision as I said, "Keep at least one of every number in every color set. Who knows what we may run into as we travel?"), he eventually used up the Key of Beginnings and we crossed the door.
Part II. Old Friends
As we walked along the room, we suddenly saw 5 cards float down and, in a flash, the card became Donald, Goofy (Sora's Friend Cards), Gregorio, Yoris, and Florina(my Friend Cards). As Sora gasped in surprise as I was merely startled. As they asked how are we doing, we said we were quite fine.
Just then, a voice said, "Keep at that and you'll be no batter off than the Heartless." and as we turned around, we saw Irvine come over and we called out his name (However, Sora, Donald, and Goofy called out "Leon", and I did not see him and when I stared at my other companions, they were also confused; something really was going on here).
"Hey there, what are you doing in this castle?", I said.
But he replied, "Castle? This is Traverse Town. And who are you anyway?" (I was not paying attention at all to what Sora had been saying to Leon who, of course, is visible only to Sora, Donald, and Goofy)
"What! What's with you, Irvine?"
"And how do you know my name? I'm afraid you are looking for the wrong guy and that he probably has my appearance."
As I muttered in grief, he then said, "Don't consider it as a personal matter, Rael."
"So you do know him! What's with you?!", Florina shouted out.
"You got a point there; I don't know what's going on in my mind."
"Psst." Gregorio said to Yoris. "Do you think this is one of his jokes?"
"If it is, its not funny. Rael was really hurt by his words."
Irvine then said, "Who's kidding around, Yoris? You and Gregorio are the ones who-"
"So you DO know our names, too?!"
"Aack! What's going on in my head?"
A voice then said, "Looks like something's going on here." When we looked at the direction of the voice, it was Rinoa (Sora and Co. probably saw Yuffie instead).
"What's going on here?", I asked her, desperate for an answer.
"No idea at all, sorry to speak. But one thing's for sure; though I do not know any of you guys, I do know your names."
And she named out each one of us (she, and the other SeeD Remnants, as I found out later, probably did not see Sora and Co. since she did not mention them). After whispering something to Irvine, she ran off. Irvine then activated the 'battle matrix' on me (Leon probably did the same to Sora) and he instructed me on 'card breaks' (I was able to see his deck now).
Whenever my card was higher then his, my shot pierced his and breached his defense (which was guarding with his shotgun), whenever it was vice-versa, his shot pierced mine, went around my shield and hit me on the back (whenever it came to other enemies, it varies). When it was a tie, our shots collided in a little 'Kaboom!" (when it came to other enemies, it's different).
He then instructed me to 'stock cards' and once I did so by willing them to do so, he then told me to use them. When I did (by willing it), a bigger shot than before came out of my gun and struck him. After warning me that stocking cards removes the first card for the rest of the battle, the matrix deactivates. Once that was done, he tossed me a blue summon card which revealed to be 'Baloo' (mighty bellow at enemies) and left. (Sora, of course, got a Simba card.) We were also given a 'Key of Guidance' as we found out later.
As Sora and I explored the Traverse Town 'floor' some more, we eventually located the 'Door of Guidance' (since it needed Key of Guidance). Once we crossed it, Sora disappeared and I was suddenly with my three companions (Gregorio, Yoris, ad Florina) and that we were in the SeeD Remnants HQ. In there, the four SeeD Remnants and talked to my friends while I pondered on the fact that if this town was a memory, everyone else here were probably memories, too.
While I was tinkering with a bunch of 'Keyblade Keychains' (created by a 'Mini-Replicator' I have in my bag and Sora's Keychains. He posed with the Keyblade with an equipped keychain and 'replicated' it. I did this while we were traveling along the road we were transported into after locking the DTD.), I overheard Quistis saying, "Probably all of your memories are helping us remember. I do not know how it works though."
Just then, the conversation was over and I was outside the 'Door of Guidance' again with Sora who was holding a "Key to Truth" keycard. The two of us then explored more of the place and soon found the "Door to Truth". Once we crossed it, I was suddenly in a black void and saw no sign of Sora. Just when I was at the verge of panicking, Sora was there once more and in front of us was Sora called "Guard Armor".
At the start of the battle, we went opposite to where he was since its feet went for us on their own but had to return to Guard Armor afterward. We then charged up at it and attacked the feet. Just then, We saw a green Mickey Emblem card and when Sora collected it, he used it. The result was Guard Armor falling apart. We took advantage of this and managed to bust all its parts. Just then the body got up again and began to spin about towards us and we evaded them as much as we could. Just then, I saw a yellow GunDelSol symbol card and when I collected and used it, the effects were the same as the Mickey card (as I found out later, only Sora can collect the Mickey cards and only I can collect the yellow cards). Soon, we defeated Guard Armor, collected the EXP, and obtained the Guard Armor Enemy Card.
After the battle, our friends were there and our Traverse Town friends were too (I presumed when it came to Sora's case). As everyone else talked to one another, I scanned my deck and adjusted it (I already obtained at least one of every Heartless so far). I took a long time scanning and by the time I was done, I was outside the Door to Truth with Sora. As we explored the 'floor' a bit more, we eventually ended up at the exit of the floor and we crossed it.