The Ass Chest (sometimes referred to as the "Gerudo RBA Chest") is an invisible chest that appears upon completion of the Gerudo Archery minigame through an upgrade oddity.
In order to play the minigame in the first place, you'll need the following:
In order to trigger the glitch, you cannot have either the Quiver (30 arrows) or the Big Quiver (40 arrows). You can either have no quiver by using bottle duplication to avoid obtaining the bow, or you can get a glitched quiver through Cojiro RBA
Once all that is set, simply play the Gerudo Archery minigame, and win twice. Instead getting the upgraded quiver, one of these 3 things will happen:
The Gerudo RBA Chest can be opened an infinite number of times if it contains the Spooky Mask or Fire Arrows. The mystery chest cutscene will always play if the Spooky Mask is inside of the chest, while the small chest animation will play if the Fire Arrows are inside and you've already obtained them. If the chest contains a Bomb Bag, and you have already gotten one, it will appear as if you got a bomb drop instead.
When giving out most items in the game, actors will call a function which writes a byte value to a specific address (0x424 from the start in NTSC 1.0) within Link's instance which determines what item is given. The table of items is known as the "Get Item" table, and is a separate table from the item table. The byte is interpreted as a signed byte value, such that positive values are awarded instantly, while negative values allow you to "open" an actor.
Because of a glitch in the Archery Gerudo actor's routine, the chest's contents is set by copying the rightmost byte of a pointer value that points at offset 0x0188 (NTSC 1.0, likely the same for all versions) into the instance of the Gerudo. By manipulating where the Gerudo actor is loaded into memory, you are able to change the contents of the chest.
Since the actor instance is aligned on a 0x10 byte boundary, the last digit of this "Get Item" byte will always end in 0x8, giving us 8 different obtainable items.
Perform the necessary steps to set up the ass chest glitch, but with the additional step of activating the Swordless Link glitch. This will allow you to get off Epona during the minigame. Then, while playing to earn the quiver upgrade score 1500 points. Dismount from Epona and exit Gerudo Fortress before the minigame is completed. There are a few different ways to do this:
When you leave the minigame without returning to the upper area of Gerudo Fortress, you store the state saying that the minigame has been completed. As soon as you enter the upper area, the Archery Gerudo is loaded into memory and unsets the completion state, making it impossible to manipulate the chest contents further, meaning you can either obtain the ass chest item, or start over.
There are several different ways to manipulate where the Archery Gerudo is loaded into memory:
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