*BIG ANNOUNCEMENT*
Alright, everypony, gather round. I have a bit of news for you. On January 8th, we will be having the group`s first discussion! This time, the topic is one fairly close to my heart (No pun intended): How Sora obtains Keychains, and
if they are simply modifiers, or new Keyblades in and of themselves.
Sure, we all know the story behind a few Keychains, like Tifa giving Sora the Fenrir Keychain after he defeated Sephiroth. But what about the others? What about Decisive Pumpkin? What about Hidden Dragon?
All this, and more, in this month`s discussion!
(Yes, we will be having discussions every month. Unless something extremely important happens that month. So if my uncle dies, or something like that, we will not be having a discussion that month.)

2546546 well my guess is when a keyhole is released as keyhole locks out fall a new and sometimes stronger keychain modifiers

P.S. this is a repeated comment with replied

2547440
That is quite the logical explanation. Mine was fairly similar. (Keep in mind that I use a lot of examples from KHII, 358/2 Days, and Chain of Memories.)
My explanation is that, when a world`s Keyhole is locked (Or unlocked, in the case of KHII and Dream Drop Distance.), a small amount of it`s power is released in the process, forming a Keychain. How does it form said power specifically into a Keychain? My guess is that the Keyholes have some form of sentience, since they will only open or close for a Keyblade wielder. Another example is that they are obviously able to hide themselves quite well. This is shown a few times in the original Kingdom Hearts:
Deep Jungle- It was hidden under a freaking swarm of butterflies. BUTTERFLIES! Like they would have the reasoning to think, "Oh, this thing is radiating pure light. We should cover it up!"
Wonderland- It was inside the Doorknob! I don`t think he swallowed a Keyhole.
So obviously, the Keyholes have sentience, since they are able to differentiate between normal people and Keyblade wielders. I mean, it must have taken some form of reasoning for Traverse Town`s Keyhole to stay hidden...