This article is about a/an transformation device in Kamen Rider Build.

"Bottle Burn!"
―Fullbottle insertion announcement in Knuckle Mode[src]

"Volcanic Knuckle! Acha!"
―Knuckle Mode finisher announcement[src]

"Cross-Z Magma! Are you ready? (Metal Gothic choral rock music) Gokunetsu kinniku! Cross-Z Magma! Achachachachachacha Acha!"
―Cross-Z Magma transformation announcement[src]

"Ready, go! Volcanic Attack! Acha!"
―Cross-Z Magma finisher announcement[src]

"Ready, go! Volcanic Finish! Achachachachachacha Acha!"
―Cross-Z Magma alternate finisher announcement[src]

"Ready go! Let's (Break/Finish)"
―Finisher Announcement in Twin Breaker[src]

The Transformation Dragon Fist Cross-Z Magma Knuckle (変身龍拳 クローズマグマナックル Henshin Ryū Ken Kurōzu Maguma Nakkuru) is a knuckleduster device used by Kamen Rider Cross-Z to transform into Kamen Rider Cross-Z Magma. Similarly to the Cross-Z Dragon, the Magma Knuckle is inserted into the Build Driver, loaded with its own Fullbottle, the Dragon Magma Fullbottle, to transform into a unique form separate from the Build Driver's standard Halfbodies. It can also be used as a weapon by Cross-Z in both his default and Cross-Z Magma forms.


After the Dragon Sclashjelly was destroyed by Blood Stalk's attack, its remains reacted to Ryuga's emotions, and transformed into the Dragon Magma Fullbottle. Seeing this, Sento Kiryu created the Cross-Z Magma Knuckle as a power-up item, and weapon as the Fullbottle was too dangerous to be used in the Build Driver alone. Originally, Sento was planning on using it himself before giving it to Ryuga, who first thought it was useless before quickly reconsidering. The Truth of the Pandora Box


The Cross-Z Magma Knuckle is composed of the following parts:

  • The CZM Volcanic Charger (CZMボルケニックチャージャー CZM Borukenikku Chājā) is a special reaction blast furnace mounted on the Cross-Z Magma Knuckle. At the time of transformation, in addition to converting the ingredients of Dragon Magma Full Bottle into the equipment's Variable Magma (ヴァリアブルマグマ Variaburu Maguma), it also has the role of generating luminescent energy for transformation and charge attacks. In addition, it can heat the captured trans gel solid at ultra-high temperature and increase its component quantity up to 4 times.
  • The Drag Burn Knuckler (ドラグバーンナックラー Doragu Bān'nakkurā) is a blow and destruction unit attached to the Cross-Z Magma Knuckle. The Dragon Sclashjelly ingredients are melted in the parts that will be the striking face, and it can take in the heat of the surroundings to raise the power of the attack. When unleashing a charge attack, light energy is emitted from the four ducts.
  • The Dragonic Igniter (ドラゴニックイグナイター Doragoniku Igunaitā) is a button used when activating a charge attack. By pushing the button, the CZM Volcanic Charger is activated, and rapid generation and compression of the light emission energy is executed. Luminous energy is emitted from the duct of the striking face at the same time as releasing the button, causing a large explosion with the impact of the attack. If a Fullbottle is loaded to the Fullbottle Slot, a special charge attack with its characteristics can be made, powerful enough to disable an enemy with a single strike.
  • The Fullbottle Slot (フルボトルスロット Furu Botoru Surotto) is a slot when a Fullbottle is inserted. It has the role of activating the Transgel Solid (トランスゲルソリッド Toransugeru Soriddo) in the loaded bottle with a special pulse and taking it inside.
  • The CZM Knuckle Trancer (CZMナックルトランサー CZM Nakkuru Toransā) is a transformation button to use when transforming. After loading the Dragon Magma Fullbottle in the slot, lifting the grip while pressing the button activates the transformation system.
  • The Magma Bray Grip (マグマブレイグリップ Maguma Burei Gurippu) is the grip part of the knuckle. The motion detection system is carried and optimizes the behavior at the time of attack by recording and analyzing the behavior of the enemy and the habit of the user.
  • The CZM Knuckle Connector (CZMナックルコネクタ CZM Nakkuru Konekuta) is a connection terminal of the Cross-Z Magma Knuckle to use for the transformation. At the same time as the Cross-Z Magma Knuckle is loaded in the Build Driver, the Drag Burn Knuckler splits open, and the driver's function expansion is executed. After that, it forms a special ladle, the Magma Ride Builder (マグマライドビルダー Maguma Raido Birudā) which is directly connected to the CZM Volcanic Charger, and it pours the Variable Magma from above the user. The Variable Magma reacts to special pulses emitted by the driver and changes to suit and armor.



The user inserts the Dragon Magma Fullbottle into the Fullbottle Slot on the Cross-Z Magma Knuckle, flips the Magma Bray Grip to the top after pressing the CZM Knuckle Transer, and inserts the device into the Build Driver, causing the Drag Burn Knuckler to split down its middle and expose the inserted Fullbottle. After cranking the Vortex Lever, the Magma Ride Builder forms and submerges the user in Variable Magma, forming eight large serpentine dragon heads which harden to solid rock as they rise. The Magma Ride Builder then breaks the hardened construct, revealing Cross-Z Magma.


Cross-Z can use the Magma Knuckle by itself as a knuckleduster weapon. In this mode, pressing the Dragonic Igniter without a Fullbottle inserted will boost the weapon's power and enable it to unleash a charged attack. This attack is several times more powerful when Cross-Z is already in Cross-Z Magma form.


The finisher accessed by the Build Driver depends on how many times the Vortex Lever is cranked.

By cranking the Vortex Lever a few times, Cross-Z Magma can perform the Volcanic Attack (ボルケニックアタック Borukenikku Atakku), which has two variations:

  • Cross-Z Magma leaps in the air accompanied by numerous Variable Magma dragons that attack the target before combining with Cross-Z for an explosive flying kick.
  • Cross-Z Magma launches several magma dragons from his arms that home in on the enemy.
  • Cross-Z Magma performs a flaming punch before becoming covered in lava, the punch is strong enough to launch the enemy.

By cranking the Vortex Lever many times, Cross-Z Magma can perform the Volcanic Finish (ボルケニックフィニッシュ Borukenikku Finisshu): Crozz-Z Magma performs a rapid series of flaming punches before becoming covered in lava and delivering a final punch strong enough to launch the enemy.

When Cross-Z Magma performs the Volcanic Finish with the Hazard Trigger attached to the Build Driver, he channels magma energy into his body and performs the enhanced version of the normal Volcanic Finish,.

By plugging a Fullbottle into the top of the Magma Knuckle before pressing the Dragonic Igniter, Cross-Z can perform the Volcanic Knuckle (ボルケニックナックル Borukenikku Nakkuru).

  • Taka: The Cross-Z Magma Knuckle projects orange energy hawk wings as Cross-Z uppercuts the enemy.
  • Dragon Magma: Cross-Z punches the enemy as the Cross-Z Magma Knuckle creates an energy projection of a dragon that pushes the target back.
  • Silver Dragon: Cross-Z uses the Cross-Z Magma Knuckle to deliver a powerful punch covered in silver flames that creates a large shockwave upon impact.

Behind the Scenes


The Cross-Z Magma Knuckle is voiced by Norio Wakamoto (若本 規夫 Wakamoto Norio), who previously voiced Rey Kivat and Arc Kivat in Kamen Rider Kiva: King of the Castle in the Demon World, and the Sclash Driver.


  • Just as the Cross-Z Dragon was the first instance of an adapter being used to access a Rider's Main Form, the Cross-Z Magma Knuckle is the first instance of an intermediary for a Driver that takes the form of a weapon (knuckleduster), and is used to access a more powerful form.
    • The last instance that most resembles the main aspects (especially the weapon type) would be the Ixa Knuckle, but to access the Main Form, instead of Cross-Z Magma Knuckle accessing the Upgrade/Final Form.
    • The Cross-Z Magma Knuckle's nature as a weapon means Ryuga can make better use of any Fullbottles he possesses, creating attacks that could not be performed by Cross-Z Dragon.
  • Cross-Z Magma Knuckle is the only intermediary/weapon to be used for an upgrade with the same Driver of the main Rider, as opposed to being part of a separate system.
    • The closest example is the upgraded Visors of Kamen Rider Ryuki, as while the intermediary is specific to the Rider, it requires the same power source for the Rider to access it.

Eight dragons manifested from Variable Magma.

  • The serpentine dragons manifesting during Cross-Z Magma's transformation sequence resemble that of the Yamata-no-Orochi, a eight-headed, eight-tailed mythical Japanese dragon.  In addition, the eight dragons are recreated into the Cross-Z Magma suit, one on the faceplate, another on the chest, two on the shoulder pads, two on arm guards, and lastly two on the leg guards.
  • Following the general theme of chemistry involved in the transformations, much like the similarly designed Magma Ride Builder, the Cross-Z Magma Knuckle could represent smelting, as both the stabilization of the Dragon Magma Fullbottle and the transformation could be seen as Ryuga extracting power from a homogenized compound.



Sento Kiryu (Takumi Katsuragi) - Ryuga Banjo - Kazumi Sawatari - Gentoku Himuro - Evolto - Nariaki Utsumi - Shinobu Katsuragi
Movie-exclusive: Kengo Ino - Killbus - Keiji Uraga
Transformation Gear
Fullbottles - Build Driver - Transteam Gun - (Great) Cross-Z Dragon - Sclashjellies - Sclash Driver - Hazard Trigger - Nebulasteam Gun - Cross-Z Magma Knuckle - Evol-Driver - Evol-Trigger - Grease Blizzard Knuckle - Killbuspider - Grease Perfect Kingdom
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nascita: Misora Isurugi - Soichi Isurugi - Sawa Takigawa - Kazumi Sawatari - Gentoku Himuro
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Aliens: Vernage
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Hokuto: Castle Hard Smash - Stag Hard Smash - Owl Hard Smash
Kaiser: Kaisei Mogami (World of Build, World of Ex-Aid)
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