Hierophant Green is an athletic humanoid with robotic features, such as the eyes and legs, but its true form is that of a long web of tentacles. It is only slightly taller than Kakyoin himself, though it can stretch itself to great lengths. Hierophant Green possesses a body covered in veiny lines, which is protected by a light-colored armor. Despite its emotionless face, it seems to have a human-looking mouth underneath its mask.
Whenever the appendages glow, the Stand is priming for an attack, such as its Emerald Splash technique.
Hierophant Green is consistently portrayed as being green across all media featuring it, befitting its name. All Star Battle features a turquoise-colored version of it. However, its armor is white-green in the colored manga and grey in the anime and games.
The series is known for alternating colors between media, the information presented below may or may not be canon.
Armor(Light mint green)
Body(Light green and black)
Hierophant Green appears to not have a personality, serving Kakyoin without hesitation or question, even seeming to act as Kakyoin's mouthpiece; although Kakyoin mentions that it hates wide open spaces and enjoys ripping things apart, such a trait is never shown.
It represents the Tarot Card The Hierophant, which represents the bridge between Heaven and Earth, relating to the Stand's long-range abilities.
Hierophant Green is the very first Long-Distance Stand shown in the series, and it has a large number of abilities to assist it in combat and scouting. However, the Stand is relatively weak in direct hand-to-hand combat, as a trade-off for its great distance-based abilities.
Hierophant using his body to ensnare enemies
As Hierophant Green's original appearance is not humanoid, but instead just a group of connected membranes, it is able to unravel itself into multiple long strings for multiple purposes such as acting like ropes, avoid damage without hurting Kakyoin himself (as shown in the battle against Death Thirteen) or weave out a network of sensitive strings that detects the enemy's movements, as during the battle with DIO.
As such, Kakyoin can control how Hierophant Green unravels, creating strong ropes or unraveling them into invisible strings. A single string has the ability to sense when someone is touching it and can attack either automatically or at Kakyoin's command. When a string is broken, Kakyoin is unharmed, but attacking a sufficient number of them or Hierophant Green's main body will harm him.
Hierophant Green is capable of sliding its coils into a person's body, allowing Kakyoin complete control of that person. This serves to protect Hierophant Green and Kakyoin from attacks if his opponent is someone unwilling to harm the innocent. Additionally, he can completely destroy the controlled being's air passage as he emerges, as well as the host's internal organs. When this ability is first used, Kakyoin is shown holding a marionette by the strings, but it is likely just for dramatic effect.
The Emerald Splash
Emerald Splash (エメラルドスプラッシュ,Emerarudo Supurasshu) is Hierophant Green's most powerful ability. It gathers energy into its body, causing it to glow bright green, before firing off a large amount of energy which takes the form of emeralds. Before the blast is fired, a green slime-like material (water-like in the anime) is produced by Hierophant Green's hands, a byproduct of the large amount of energy the attack is giving off.
The blast's range and shotgun-like dispersion, along with its incredible destructive power and high speed, make Hierophant Green an extremely capable combatant. Interestingly, it seems that though this blast is quite powerful, it doesn't seem taxing on either Kakyoin or Hierophant Green. However, the likes of Star Platinum or even a Vampire can easily block or deviate the attack.
During the original run of Kakyoin's introductory arc in Weekly Shonen Jump, his Stand's name is written as "Hierophant Emerald" (法皇の緑 (ハイエロファントエメラルド),Haierofanto Emerarudo). The name was rewritten as Hierophant Green (ハイエロファントグリーン) after Kakyoin joined Jotaro's party, though it was corrected entirely in the tankōbon release of the aforementioned arc.
Hierophant Green ended up green because Araki wanted some color balance between the allies and enemies. Green reminded him of melons, and he was really into green at the time as he used the color in several illustrations.