Dungeon ID swapping

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In vanilla ALttP, Hyrule Castle and the Sewers are considered different dungeons. When you pass through the door between the throne room and the sewers, the game changes the ID of the dungeon you're in by XORing it with 2. This is a symmetrical operation, so it creates pairs of dungeons you can swap between if your dungeon ID is not actually Hyrule Castle.

Dungeon ID swapping can allow you to collect the prize (crystal or pendant) of a dungeon without ever entering it. It's important as a way to complete Misery Mire (NL) in No Logic without having the correct medallion for it.

Dungeon IDs that can be swapped with each other
Dungeon 1 Dungeon 2
Hyrule Castle Sewers
Eastern Palace Desert Palace
Tower of Hera Thieves' Town
Hyrule Castle Tower Swamp Palace
Palace of Darkness Misery Mire
Skull Woods Ice Palace
Turtle Rock Ganon's Tower

(links are to the No Logic guides for these dungeons)

If you're in cave state, the dungeon ID becomes $FD, which is an alternate cave state in the vanilla game, and crashes in the randomizer.

Almost all setups for dungeon ID swapping (besides playing Hyrule Castle as intended) need to come from the sewers and go back and forth through the throne, so you need to do sewer door deletion first.

The usual route

A diagram of the dungeon-swapping route that starts and ends in Hera

Keep in mind the prerequisites to dungeon ID swapping:

More images of the steps appear in this imgur post.

1. Bomb clip from Hera to the sewer

  • In the southeast room of Hera 3F, place a bomb to the upper right of the crystal switch.
  • Dash rightward along the slope into the bomb, and hold ^< during the knockback.
  • You clip through the slope into the dark sewer.
Line up against the top edge of the crystal switch, with your shadow centered on the vertical edge between tiles, and place a bomb.

2. Pass through the sewer/throne door

If you have performed sewer door deletion, the shutter door at the south end of this room isn't really there anymore. Go through it into the throne room, then go back through it into the sewer.

Alternative, you can hookpush thought the wall with the closed door.

Lit room in practice hack

This is the moment that your dungeon ID swaps. If you have a compass and dungeon counters are on, you may see the dungeon counter change.

3. Proceed through the sewers

Play the game normally until you get to the key-rat room.

4. YBA/Hookpush to get back into Hera

From the key-rat room:

  • Do a south subtile YBA (drinking a red or green potion at the moment you go through the door)
  • Tap left or right about 5 times, to back out at least 5 pixels while staying in the door.
  • Pass through the door, and emerge from the top wall of Hera 3F.

Sprites (such as enemies) are likely to despawn in this step. If Moldorm is already defeated, you can head to the top floor to claim your dungeon prize.

Alternative, you can hookpush thought the wall with the closed door and you can go back to Hera.

Lit room in practice hack