The Grateful Dead
It has the simple but deadly ability to rapidly age any living organism, with the rate of aging being proportional to the organism's body temperature.
The Grateful Dead appears as a humanoid torso with long arms, large hands, and numerous angled eyes of various sizes embedded all over its face and body. Its face in particular has three horizontal or diagonal eyes on each side, with one larger vertical eye on the center of its forehead, and two horizontal eyes on the back. There are four horizontal eyes on its chest and back, with several more on its arms. It was designed with these multiple eyes to make it resemble a yokai. Although it lacks a mouth, it has an oval-shaped protuberance extending from the center of its face to its chin. The anime adaptation also changes the shape of its fingers, being more claw-like in appearance.
There are screw holes in its shoulders, elbows, and wrists. Lacking a lower body, there are four segmented tentacles hanging from its waist instead. Rather than floating, it directly walks on the ground with its hands, with three huge metal-like segmented fingers evenly spaced around its circumference. Araki originally intended to draw the lower half of its body but changed his mind, thinking it looked fine as it is and appears more unusual this way. The Grateful Dead represents how Araki chooses to design Stands based on their functionality. Since it doesn't have a physically-based ability and wouldn't need to punch, Araki removed the functionality of the Stand's hands by making them function as legs instead.
The Grateful Dead constantly emits a light mist from its body when activating its ability.
The Grateful Dead's greatest asset is its ability to forcefully age people over a large area, making it a terrifying power because of its potential for a massacre.
However, the aging can be slowed, and while The Grateful Dead isn't weak, it isn't a match for other close range Stands like Sticky Fingers.
The Grateful Dead has the ability to cause organisms to age physically and mentally at an accelerated rate.
There are two ways The Grateful Dead can deploy its power. The first mode is to spread the aging over a large area and indiscriminately attack friends and foes, which is dangerous for Prosciutto's companions. The second mode is to direct its power precisely by grabbing someone, in which case the aging is faster than one can react. The activation of this ability manifests itself as mist spreading from The Grateful Dead.
When under the effect of The Grateful Dead, people age rapidly with all the effects it implies: their skin develops wrinkles, their teeth begin to fall out, the tips of the limbs start to necrose, the bones and joints shrink, and their cognitive ability is reduced. Infants would succumb to the effect of "aging", with their skin wrinkling and hair falling out, rather than merely growing into an adult quickly. Even fruits and flower wither and dry up.
Because the spirit is also aged by The Grateful Dead, enemy Stands are also weakened. Their power and stamina are sapped, and even a powerful close-range Stand like Sticky Fingers can become slower than the rather slow The Grateful Dead.
Prosciutto is normally immune to The Grateful Dead and can stay young inside its range. However, he can freely toggle the aging on himself, notably fooling Mista into thinking he's a mere civilian.
The rate at which people age is dependent on their body heat. The warmer one's body is, the faster they age. Because of minute differences between men and women's bodies, women also age more slowly. Thus things warming the body like intense physical activity will accelerate the aging but exposure to cold, like ingesting ice, will counter and reverse The Grateful Dead's power immediately, although both effects balance themselves and insufficient coldness will not have an effect.
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