The Zodiarts are the antagonists of Kamen Rider Fourze. Each of the Zodiarts is themed after one of the 88 Western constellations, and each Zodiarts' body is decorated with the pattern of the constellation it is named after. The name "Zodiarts" is derived from the English word "zodiac".
Reverse engineered from the Core Switch to reach the alien race known as the Presenters, the Zodiarts Switches which are made from Cosmic Energy, are designed to force-evolve the user, the Switcher, into a being that can survive the void of space. The result of the transformation is a Zodiarts, a monstrous construct of Cosmic Energy.
After the Zodiarts Switch is used several times in a row or when the Switcher is enraged enough, it will announce "Last One" and the Zodiarts Switch will change its appearance, growing spikes and an eyeball-like structure, as well as changing the position of the button. When the Switcher activates the Switch at this point, the transformation becomes irreversible as the Switch drains its Switcher of their conscious mind and uses it to become a Zodiarts permanently. The Switcher's empty body is ejected from the Zodiarts, covered in a cobweb-like substance. In this state, a Zodiarts becomes extremely powerful to the point that its destruction would cause a massive explosion that would destroy everything surrounding it. A Zodiarts, especially one at its strongest, can only be defeated if targeted at point of its body where the Zodiarts Switch is located. From there, Kamen Riders Fourze or Meteor can use one of their Limit Break finishing attacks to destroy the monster and get the Zodiarts Switch.
Once properly switched off, the Zodiarts Switch will vanish into a singularity, keeping its user from ever becoming a Zodiarts again. However, it is still possible for a Switcher to become a Zodiarts again through another Zodiarts Switch. It also appears that a Switcher gains an addiction to Cosmic Energy after using a Switch, which only helps in making them Zodiarts again. Also, if a former Switcher has obtained Last One previously, their new Zodiarts Switch will automatically assume it's Last One form. Combined with the threat of evolution, this would be a quick way for some Horoscopes to be born through former Switchers.
Zodiarts are collectively named after the "Zodiac".
Several Zodiarts, along with Dopants, Yummies, and Phantoms, were part of the Monster Army, a hoard of kaijin who were revived by the Akumaizer to conquer humanity. They were defeated by a group of eight Kamen Riders consisting of Kamen Rider Wizard, Fourze, Meteor, Nadeshiko, Double, Accel, OOO, and Birth.
The end result of Mitsuaki Gamou's research for a means to reach the Presenters, the Horoscopes are evolved Zodiarts that transcend human nature. A Horoscope manifests whenever a Resurrection Star on the body of a Zodiarts in its "Last One" stage glows. Once the evolution happens, once brought to it, the Zodiarts' original human body is turned into Cosmic Energy and absorbed back into the Zodiarts' body as the new-born Horoscope molts out of its old Zodiarts body as it dissolves into Cosmic Energy. In some cases, the evolution occurs faster with those who already obtained the potential and need to only use a Zodiarts Switch once to transform, bypassing the Last One stage. Gamou's goals are related to gathering all twelve Horoscopes Switches together.
- Orion Zodiart
- Chameleon Zodiart
- Unicorn Zodiart
- Hound Zodiart
- Altar Zodiart
- Pyxis Zodiart
- Perseus Zodiart
- Canis Minor Zodiart
- Lynx Zodiart
- Dragon Zodiar
- Pegasus Zodiart
- Cygnus Zodiart
- Coma Zodiart
- Musca Zodiart
- Hercules Zodiart
- This is the first kind of monsters faced by a Rider to have the plural suffix be the official name.
- The Zodiarts are similar to the Dopants in how they are humans powered by dark versions of the Kamen Riders' power source. Unlike the Dopants, getting rid of a Zodiarts requires the Zodiarts Switch to be manually switched off instead of it being destroyed after defeat.
- Canis Minor is the only Zodiarts shown so far to have it's name be in kanji format.
- There has been four Zodiarts that appeared the following episode after they were defeated by a Limit Break: the Orion, Perceus, Lynx, and the Pegasus Zodiarts.
- Miura is played by Masanori Mizuno, who had previously portayed Jun Watari AKA Fire-5 of Rescue Fire, the second and final edition of the extremely short-lived Tomica Hero Series.
- Ritsuko is played by Hikari Kajiwara, who had previously worked in a Kamen Rider Series installment as Amane Kurihara in Kamen Rider Blade.
- The voice of the Cygnus Zodiarts is Taiki Matsuno, who previously worked in a Super Sentai Series by voicing Sky Ninja Shurikenger of Ninpuu Sentai Hurricaneger.
- Yayoi is played by Kasumi Suzuki, who was also part of a Super Sentai Series, but as Bakuryuu Sentai Abaranger villain Disciple of the Dawn Lije.
- Jirou Iseki is played by Ryuusei Yokohama, who would later portray Hikari in Ressha Sentai Tokkyuger