You can use Trinity Ladder in a bunch of worlds, but most importantly in Neverland to progress the story, and in Traverse Town to access the Moogle Shop for Item Synthesis.
All Green Trinity Locations
There are a 9 total spots throughout the game where Sora, Donald, and Goofy can use Trinity Ladder. Here’s a full list of ever spot with screenshots:
Traverse Town (Accessory Shop)
Look in the middle of the floor in the Accessory Shop. Activating this trinity will lower a ladder above you. This will grant you access to the Moogle Workshop, where you can perform synthesis to craft lots of items, accessories, and even some custom weapons.
Wonderland (Rabbit Hole)
Look near the spot at where Sora enters at the beginning of the world (you’ll need to turn yourself big in the Bizarre Room first). Activating this trinity will get you an elixir.
Wonderland (Bizarre Room)
Get back to the Bizarre Room, but make yourself tiny again and then look inside the fireplace located on the right-hand side of the room. This trinity will give you a Mythril.
Olympus Coliseum (Coliseum Gates)
Look just left of the main entrance, right in front of the Rankings board. This Green Trinity will also give you a Mythril.
Deep Jungle (Treetop)
This can be hard to find since all the leaves and plants around you will also be colored green. Just look close to the center of the area – if you’re in the Treetop then you’ll definitely find it (look at our screenshot for reference). You’ll be rewarded with a Mythril Shard and HP orbs.
Agrabah (Storage Room)
Go to the very “end” of the streets in Agrabah, but before you leave to the Cave of Wonders. You should find a Storage Room off to the side of this street area. It’s a tiny room so you basically can’t miss this Trinity mark – but look in front of the shelf in the room to find it. This will give you a Power Up in the original game on PS2, or you’ll get an AP Up in KH1.5/Final Mix.
Monstro (Mouth)
This trinity does require the High Jump ability. But once you’ve unlocked it you should be able to equip this in your Shared Abilities, then jump up on top of Geppetto’s ships (right on the roof) and you should see a green mark. This will give you a Mythril Shard. If you can’t seem to get up on top with High Jump then you might want to learn Glide first, since gliding over to this spot is much easier.
Neverland (Cabin)
Look right in the middle of the cabin’s floor – you really can’t miss this one. It’ll grant you access to the Captain’s Cabin to progress the story, so this Trinity Mark is basically required to get through the game.
Hollow Bastion (Library)
On the second floor of the library, look where the table and save point are. This will let you reach a book that’s up on top of a bookshelf to progress the story.
