O Medals

Medals (メダル), referred to, for clarity, as O Medals (オーメダル), are special coin-like medals that are the center of Kamen Rider OOO's different powers based on the animal the Medal represents. There are two different types of O Medals: Core (コア) and Cell (セル).

Core Medals
Core Medals (コアメダル) are colored O Medals that make up the essence of a Greeed. They can also be used to transform into Kamen Rider OOO or any Combos. These five types of Core Medals were originally fifty (five sets of ten) created by human alchemists 800 years ago as a means to create artificial life, drawing from characteristics of different animals, forming the core of the Greeed before one Medal in each set was taken. With the tenth medal gone in order to create a 'desire' in the nine other medals, the Greeds were created. A sixth set was also created, the Purple Cores, which are made from the antithesis of desire. Later Core Medals were created with current and future technology which seemingly surpass previous Core Medals in power. It is also notable that Foundation X somehow managed to turn Kamen Riders themselves into Core Medals.

Each set of Core Medals comes in a specific color and animal type. Red Core Medals have bird powers; yellow Core Medals have big cat powers; green Core Medals have insect powers; silver Core Medals have heavy mammal powers; blue Core Medals have marine animal powers; purple Core Medals have dinosaur powers; and orange Core Medals have reptilian powers. There are 70 Core Medals total from the series, each three from a Greeed divided in three groupings for the use of OOO: Head, Arms (Torso), and Legs.

Ankh= Ankh's Core Medals are red. Being of avian nature, they have bird powers. OOO can use three of them to change into the Tajadol Combo, granting him the Kujaku Wings to fly and fire peacock tail feather energy projectiles at opponents. A total of ten existed in the modern world, with the tenth, the King's medal, in the secret possession of the Kougami Foundation. In , a set of these Medals are combined into the Tajadol, which is used by Captain Marvelous (Gokai Red) to into OOO's Tajadol Combo.
 * Taka Medal (タカメダル): The Taka Medal is the Hawk-themed O Medal given to OOO by Ankh. As a Head Core Medal, it allows OOO to use the Taka Head, greatly improving his senses and improve his accuracy. It also enables him to see inside Greeed or Yummy, such as pinpointing the location of a specific Core Medal within a Greeed's body, which was shown when he used the Taka Medal to find the Shachi Medal in Kazari's body. In Tajadol Combo, the Taka Head becomes the Taka Head Brave (タカヘッド・ブレイブ). It was the first Core Medal to be seen in the series. After Ankh's sacrifice, only one of these remained before it broke into two halves while the last intact copy was sucked into a black hole. Following the loss of all the other Core Medals to the black hole, this is the only Core Medal to still exist in some form in present day, the broken halves taken by Eiji on his travels. After Super Hero Taisen, Eiji now has the sole remaining Taka Medal, but he still needs to get Ankh's broken Core restored. When changing into Combos, the name would take the first kana for main Combos and the entire name for Random Combos.
 * Kujaku Medal (クジャクメダル): The Kujaku Medal is the Peacock-themed O Medal. Until episode 20, Kazari took it for himself until Ankh stole it from him after making a diversion. It allows Kamen Rider OOO to use the Kujaku Arms, equipping him with the Taja Spinner. Ankh finds another copy of this Medal during the events of Movie War Core. After Ankh's sacrifice, the remaining two copies are sucked into the black hole that was caused by the destruction of the Kyoryu Greeed. After Movie War Mega Max, Eiji has one of three of this Medal. When changing into Combos, the name would take the second kana.
 * Condor Medal (コンドルメダル): The Condor Medal is the Condor-themed O Medal. It allows Kamen Rider OOO to use the Condor Legs, allowing him to use talon-like attachments to enhance his kicking damage. Ankh found one during the events of Movie War Core. In the series, it was revealed that Kougami has one of three of this Medal, and intended to give to Eiji, but he declined so Ankh wouldn't leave Shingo's body to die but was later used during the fight with the Lion-Kurage Yummy. After Ankh's sacrifice, the remaining two copies are sucked into the black hole that was caused by the destruction of the Kyoryu Greeed. After Movie War Mega Max, Eiji has one of three of this Medal. When changing into Combos, the name would take the last two kana.

Cell Medals
Cell Medals (セルメダル) are silver O Medals and come from the Greeed, but also make up the bodies of the Yummy. These Medals are a manifestation of human desire that hold tremendous power. While the Greeed were sealed away, the Kougami Foundation studied and gathered the Cell Medals, incorporating them in their Ride Vendor, Medajalibur, and Candroid technology. Whereas Core Medals can be used and reused without effect done on the Medals, Cell Medals only have a limited amount of energy and vanished when the energy has been depleted.

Unlike Kamen Rider OOO who uses Core Medals, Birth uses these Cell Medals to transform or access weapons. These Medals can be used to transform into Birth or used in a Cell Burst. No specific Cell Medal is required for Kamen Rider Birth to transform, summon a Birth CLAWs armament, or initiate a Cell Burst attack. Unlike OOO's Core Medals, Cell Medals can only be used once. After said use, their energy is depleted, and they fade away. Also unlike OOO's cores, which can only be destroyed, Cell Medals can be broken, as demonstrated by Uva and Poseidon's shattering Cell Medals to make Waste Yummies.

Legend Rider Medals
X Medal (Xメダル), Amazon Medal (アマゾンメダル), Stronger Medal (ストロンガーメダル): Core Medals representing three of the seven sealed Kamen Riders which appear during the events of Kamen Rider × Kamen Rider Fourze & OOO: Movie War Mega Max that, along with the 1, 2, V3, and Riderman Astroswitches, are in Foundation X's possession. Kamen Rider OOO is able to release the Riders by putting them into the OOO Driver and scanning them which activates a Scanning Charge. These Medals are based on the Legend Rider Medals (レジェンドライダーメダル) which used to be compatible with the Kamen Rider Battle: Ganbaride arcade game.

Further History
In the series finale, only 53 Core Medals that remained after Eiji and Maki permanently killed several of the Greeed. However, all Core Medals except for one Core were thought destroyed when Eiji was able to defeat the Kyoryu Greeed, the Greeed absorbing all but one of the Core Medals, along with the Medal Vessel. The influx of power caused a black hole-like collapse of the Purple Core Medals' power, seven of the Purple Cores seen shattering as they approached the event horizon, disappearing forever. That one Core Medal that was left is the split-in-two Taka Medal which formerly contained Ankh's consciousness, Eiji now carrying it with him on his journey while find a way to fix the medal and revive him. However, in the Kamen Rider × Kamen Rider Fourze & OOO: Movie War Mega Max, it was eventually revealed that the black hole was not a gateway to destruction, but a time portal, which had sent all of the Core Medals, as well as the Cell Medals, the Medal Vessel had gathered, inculding what could possibly be the remains of the Kyoryu Greeed's consciousness, 40 years into the future. There, they merged into the body of Michal Minato. The overwhelming amount of Cell Medals and Core Medals allowed the newly created medals of Kamen Rider Poseidon to form into a Greeed with a will all of its own.

There were also the King's Core Medals (王が持っていたコアメダル), which were originally part of the Core Medal sets that composed Ankh, Kazari, and Uva. Being the only tenth Core Medals separated from the rest of their respective sets instead of being destroyed, the King used them to become Kamen Rider OOO eight centuries ago. They were originally in Kougami's possession until he gives them to Eiji to become the true Kamen Rider OOO. These special Cores were first mentioned in a Foundation X report during the antepenultimate episode of Kamen Rider W, referred to as the King Medal (at the time, it was believed there was only one King Core) which are said to have more power than even the True Gaia Memory. However, prior to the final battle, the King's Core Medals shattered due to the power of the purple Core Medals and the massive amount of Cell Medals in Eiji's body.

After Mega Max, Eiji now has one copy of each Core Medal of the five desire-based Medals. However,  had shown that Eiji has regained the Purple Cores, with only seven of the Core Medals being explicitly been shown destroyed in the finale and never seen/used in Mega Max. Also, Eiji was seen to have two more copies of the Taka, Tora and Batta Medals to allow Gokai Red, Yellow, and Green to assume his Tajadol, Latorartar, and Gatakiriba Full Combo forms. In Ultimatum, Eiji uses the orange Core Medals, bringing his total count of Medals to 28.

The O Medals, along with the other Rider Powers, were stolen from OOO by Amadum in the world within the Magic Stone, who explained that they were already his due to the Riders' powers being from the same source as evil. However, the power was soon returned thanks to the appearance of Kamen Rider Gaim, with the return of the Medals immediately transforming OOO into Super Tatoba Combo.

Toy-exclusive Medals
In Kamen Rider Battle: Ganbaride, toy versions of the O Medals, both Core and Cell, can be used with the OOO style Ganbaride arcade machines to either change combos or initiate attacks. Some are also exclusive to the game such as the Legend Rider Medals that allow Kamen Rider OOO to transform into the Kamen Riders based on those Medals and perform their finisher attacks. Many of these Medals sport different colors, with sporting the main Rider's emblem to show which series they hail from.
 * Showa Era Medals
 * 1
 * Shocker Rider Number 1
 * 2
 * V3
 * Riderman
 * X
 * Amazon
 * Stronger
 * Skyrider
 * Super 1
 * ZX
 * Black
 * Shadow Moon
 * RX
 * Heisei Era Medals
 * Kuuga (Mighty/Dragon/Pegasus/Titan)
 * Agito (Ground/Trinity/Burning)
 * Ryuki
 * Knight
 * Ouja
 * Ryuga
 * Faiz (Normal/Axel/Blaster)
 * Kaixa
 * Blade (Ace/King)
 * Garren
 * Chalice
 * Hibiki (Normal/Kurenai)
 * Kabuto (Rider/Hyper)
 * Gatack
 * Dark Kabuto
 * Den-Liner
 * Imagin (Momotaros/Urataros/Kintaros/Ryutaros/Negataros)
 * Den-O (Sword/Rod/Ax/Gun/Liner/Super Climax)
 * Zeronos (Altair/Zero)
 * Nega Den-O
 * New Den-O
 * Kiva (Kiva/Garulu/Dogga/Basshaa/DoGaBaKi/Emperor)
 * Ixa (Save/Burst)
 * Decade (Normal/Complete/Violent Emotion)
 * Diend (Normal/Complete)
 * Neo-Heisei Era Medals
 * Double (CycloneJoker/HeatMetal/LunaTrigger/FangJoker/CycloneJokerXtreme/CycloneJokerGoldXtreme)
 * Skull (Skull/Crystal)
 * Accel (Normal/Trial/Booster)
 * Eternal
 * Joker
 * 11 Riders