Stone Mask

The Stone Masks (石仮面) are powerful ancient artifacts featured in the first two parts of JoJo's Bizarre Adventure, Phantom Blood and Battle Tendency. They were originally introduced as sacrificial devices used by certain Vampiric cults hidden within the Aztec Empire.

Mounted ornamentally in the Joestar family estate by George Joestar I, one Stone Mask eventually transforms Dio Brando into a Vampire, extending his life, as well as his influence over a significant proportion of the series.

In Part 2, it is revealed that the Stone Masks were designed by Kars in an attempt to grant his race the ability to withstand sunlight.

Appearance
The conventional Stone Mask has the appearance of a somewhat-masculine face, its eye holes sharp and somewhat slanted. It has a small mouth in either a neutral position or a slight smile, with full lips, and small fangs resting on the bottom lip. A ridge emerges from the bottom of the forehead, running vertically to the Mask's top, joining with another ridge extending into a spiral resting on the left of its forehead.

The Stone Mask owned by George Joestar I, bore four short lines of writing on the reverse side of the forehead. Written in an obscure, semi-cursive script, the significance of the writing is unexplained. The Masks featured in the story also commonly exhibit cracks and other signs of wear, likely due to their age.

Kars' modified Stone Mask has a raised depression in the middle of its forehead, in the mold of the Red Stone of Aja.

Background
Between the 12th and 16th century, an ancient Aztec ritual took place in Mexico, where a man wearing a Stone Mask sacrificed a young woman. The man's tribe tried to conquer the world with the help of the Stone Mask and its powers, before suddenly disappearing from history.

During the mid-to-late 19th century, one Stone Mask was excavated from an Aztec ruin by a team led by William Anthonio Zeppeli's father. After donning the mask himself, the Zeppeli slaughtered his crew and died from the sun, leaving the mask to drift into the unknown.

The same mask eventually lands itself in the possession of aristocrat, Mary Joestar, who had purchased it during her travels. After her death, the mask is retrieved by her husband, George Joestar I, who mounted it on a wall in his family home.

Phantom Blood
The Mask later becomes the subject of research by Jonathan Joestar during his study as an archaeologist, who is unable to understand its purpose and only able to come up with speculative theories.

These theories attracted the morbid curiosity of Dio Brando, who believed it to have been an execution item that he could attempt to use on Jonathan. After testing it on another human, he realizes that it transforms them into Vampires.

When Dio's crimes were exposed, he stabbed George and used his blood to activate the Mask on himself. This transformed Dio into a Vampire, enabling him to further torment both Jonathan and his descendants.

Battle Tendency
In Part 2, a collection of Stone Masks surround the sites of the Pillar Men's slumber; both with Santana in Mexico, and with Wamuu, Esidisi and Kars in Rome.

It is revealed that Kars is the original creator of the Stone Masks. He intended to use them to give himself and/or his race the ability to withstand sunlight, only to discover that the Mask's tendrils were unable to push their brains further, due to their immortal bodies. Theorizing that he required greater power to strengthen the Mask, he designed a modified version meant to be combined with the Red Stone of Aja. Kars kept this version of the Mask with him during his long search for the Stone, eventually succeeding in combining the artifacts and becoming the Ultimate Being. This Mask was destroyed after Kars's transformation.

Vampires
The Stone Mask is triggered when it is touched by blood. It then extends tendrils of stone from its edges, piercing the wearer's skull and brain. The tendrils are meant to find and trigger certain precise points of the brain; the process is described as being similar to acupuncture.

The Mask's wearer is then released from the constraints of natural limitation, gaining immense strength and other abilities. This vampirism process has been shown to work at least on humans and horses.

According to Robert E. O. Speedwagon, humans who wear the mask have their jumping ability increased by '5/8' meters, their punching up to 2000-4000 kg/cm2, and their leg strength tripled. However, the process simultaneously renders the body "dead" (in a sense) or unable to contain life, giving them a weakness to direct sunlight or the Ripple. This collection of effects designates the wearer as a Vampire.

Pillar Men
Pillar Men who wear the mask are given enhanced abilities and invincibility, but require even more energy from other living creatures to sustain themselves. Using this augmented form, Kars was able to wipe out his entire clan.

To unlock further power, Kars created a modified Stone Mask which, when fitted with the Red Stone of Aja, had the ability to pierce a Pillar Man's skull completely. This Mask is triggered by exposure to intense light, such as the UV beams released by the Nazis' anti-vampire weaponry.

In this case, the Mask unleashes a retrograde effect, in which Pillar Men are completely immune to the Sun, gain the ability to use the Ripple; and morph their bodies on a cellular level into any creature (preexisting, and new, conceivably). The Mask itself is destroyed in the process, likely due to the immense amounts of power emitted by the Red Stone.

It is unknown what effects would occur if a human, or a vampire, were to wear the Aja-enhanced Stone Mask.

Trivia

 * As one of the most famous items in the series, the Stone Mask has appeared in several games:
 * In Heritage for the Future, as part of the "Stand Crush", when one of the players has their Guard Gauge broken by the opponent, the Stone Mask briefly appears on the screen.
 * In Phantom Blood (PS2), before every match begins, the Mask gains life for a short time and its tentacles comes out, announcing the episode start.
 * It appears in All-Star Battle as the representing item for PART I arc in several trailers and Story Mode.


 * Various games in the Castlevania series have an item called Stone Mask (sometimes called Jade Mask), which, according to in-game descriptions, were used in ancient rituals; a seemingly clear reference to JoJo. Appropriately, vampires are a central element of the Castlevania universe.