Memoria

Memoria is a pseudo-world made of people's memories. It can be accessed from Archivio by the Sky Priestess.

Because Memoria is based on somebody's memories of a given location, it is usually slightly different from the real version. This applies even to things that the originator recognizes is incorrect, and is not corrected even when they point it out.

Memoria is formed based on Mukashic Cubes, which store the Mukashic Record of people's memories, and is physically built out of Memoria Cubes (メモリアキューブ), which act as both a core of the world and a gate back to Archivio. However, the extraction of Mukashic Cubes removes the related memories and abilities from that life form's mind, significantly weakening them and causing them to forget details (though, notably, general information is retained). To recover this information, the individual must travel through the Memoria, reliving their experiences (albeit altered).

When a Memoria is generated, the originator of the memory is removed from its world, allowing them to travel inside and take their place. However, due to the intensity of memories, memories of people appearing in Memoria are much more powerful than they were in the real world.

Though unexplained, it has also been shown that memories of people inside a Memoria can resonate with the Sky Priestess' Mukashic Cubes, forming memories of people from their own past and incorporating them into the current Memoria. This seems to occur in times of heightened emotion, and the newly formed being dissipates when their originator calms down.

Memoria's state after the destruction of the Divine Breath and Large Mukashic Cube is unclear.

Hysteria
Hysteria (ヒスタリア) are Frayed Memories (記憶のほつれ) in a Memoria. They are particularly distorted bits of memory, causing rips in the world of Memoria. To resolve them, the originators must enter the rips and correct issues plagueing them. However, not all originators can enter the Hysteria; some will simply walk through the tear in space without entering it.

If somebody enters a Hysteria and is unable to solve the problem within it, they are incapable of leaving, becoming permanently trapped inside.

Due to being so heavily distorted, they only slightly resemble the actual memories of the location, and merge memories of multiple events. They also only contain a small area, which is limited by the bounds of the unclear memory. Notably, Hysteria reflect the Memoria world without any changes made by the originators.

Trivia

 * The reason for Zaraza having an alternate persona inside Hysteria is unclear. This quirk is unique to him, as other characters appearing both inside and outside Hysteria all maintain their normal selves.

Archivio
Archivio (アルチビオ) is the connecting point between Memoria and the real world, and is where somebody's body remains when they enter Memoria. It is made of elements generated by the Tower of Heaven, and is used to store Mukashic Cubes.

Mukashic Cubes
Mukashic Cubes (ムカシックキューブ) are the crystallized form of Mukashic Records (ムカシックレコード), which represent a life form's memories. Mukashic Cubes can be extracted from a life form by the Sky Priestess, and only hold their shape within a 10 km range of the Tower of Heaven on Waford.

There is also a type of Mukashic Cube called Record Cubes (記録キューブ), which store a person's memories in a readable format. They can be created by Ninja Yoisa, even without the recipient's permission.

Their name is likely a reference to the Akashic records (アカシックレコード), a compendium of everything that ever has or will occur. Mukashic Records is written with nearly the same kanji, with the difference, replacing Akashi (アカシ) with Mukashi (ムカシ), implying that it focuses on the past, as mukashi roughly translates to "former" or "olden days".

In the English version of One Piece Odyssey, they're called Olassic Cubes and Olassic Records respectively.

Large Mukashic Cube
In the Tower of Heaven there lies the Large Mukashic Cube (オオムカシックキューブ), which is used by the Divine Breath to store the information it learns, and stores the "brain" of the Divine Breath. It is the source of all Mukashic and Memoria Cubes, and can turn Mukashic Cubes into the memory they transcribe. Alongside the Divine Breath, it acts as the main antagonist of the One Piece Odyssey expansion Reunion of Memories.

In the English version of One Piece Odyssey, it is called the Large Olassic Cube.

Past
At some point in the past, Rita Suerte stored her memories in a Memoria to create the Sky Priestess' trial.

One Piece Odyssey
After having their memories removed by Lim, the Straw Hat Pirates traveled through their past adventures in Memoria.

Reunion of Memories
Having awoken from its slumber, the Large Mukashic Cube forced the Straw Hats into modified Memoria, intent on studying their reactions. It was ultimately destroyed by the Straw Hats, while the state of Memoria as a whole is unknown.