This page serves as documentation for the game's many triggers and flags. It goes over what they unlock, the requirements to unlock them, and sequence break information.
Zelda gives out the Special Charm when you encounter her in Hyrule Castle. This is needed for two reasons:
It also enables you to talk with Sahasrahla in his house in Kakariko Village.
Defeating Yuga in Eastern Palace activates the Barrier around Hyrule Castle.
It also causes the Irene Triggers to appear around Hyrule so that you can get the Bell, Gulley's Pouch to be available in the Haunted Grove, and Rosso's House to be open (with the rocks appearing around it) so that you can receive the Power Glove.
Having the Pendant of Courage in your inventory opens the door leading to Inside Hyrule Castle. The loading zone will not be present otherwise.
Note that it is possible to complete Eastern Palace without obtaining the Pendant of Courage.
Despite the game suggesting you need 3 Pendants to acquire the Master Sword, it actually only checks for 2. If you perform Pendant of Courage Skip and then complete House of Gales and Tower of Hera, you'll be able to enter the Lost Woods to retrieve the Master Sword with just the Pendants of Wisdom and Power.
As stated above, you only need the Pendants of Wisdom and Power to retrieve this.
Having the Master Sword in your inventory unlocks the ability to buy items from Ravio's Shop, and will cause him to give you the Quick Equip ability the next time you enter and leave the shop.
Hyrule Castle acts like a giant combination lock guarding the entrance to its Dungeon, "Inside Hyrule Castle," which is the critical path forward to unlock Lorule.
There are several gates to pass in order to reach the loading zone to Inside Hyrule Castle:
Ravio's Shop is actually activated in stages:
Complete the Sanctuary. This causes Ravio to start crashing at your house and give you his Bracelet.
View Ravio's Signs in Eastern Ruins. Watching the short cutscene of the signs and then returning to the Shop will cause Ravio to give you the Bow for free. The signs themselves will only appear after completing the relevant Prologue Triggers, detailed in an earlier section.
Fully Activate the Shop. There are 3 ways to fully open Ravio's Shop:
Ravio's Shop can be opened early, even if you haven't yet watched the Signs cutscene, in one of two ways:
More information about the Shop and item sale prices is available on this page: Ravio's Item Shop
You must visit Ravio's Shop at least once after it's been fully opened for the Rupee Rush minigame to open as well.
In order to play Hyrule Hotfoot you must first encounter Irene at any of her triggers.
Running into the Shady Guy as he runs out of Zora's Domain will cause the Street-Merchant in Kakariko to sell the Smooth Gem, and the Shady Guy himself will also be there for you to sneak up on to receive the Pegasus Boots.
There is a special trigger inside the boss door of Thieve's Hideout that checks that the player has the Thief Girl with them, and if they do it will spawn Stalblind and begin the boss fight.
The loading zone for Thief Girl's house will not appear until after Stalblind has been defeated.
You need 7 Sage paintings to activate the Hilda trigger outside of Lorule Castle. In addition to opening Lorule Castle and placing its loading zone on the map, it will also place the loading zone for the final boss battle.