"Number C", short for "Chaos Numbers" (
So far, all "Chaos Number" monsters, if they are Summoned normally rather than by Chaos Xyz Evolution, require one more material than their normal versions. The first two "Chaos Numbers" require the same Attribute as the Attribute of their base form and necessitate the user having 1000 or fewer Life Points in order to activate their effects. The rest require a "Rank-Up-Magic" Spell Card, or in rare cases, another card capable of performing a Rank-Up such as "Don Thousand's Throne". Furthermore, with the exception of "Number C39: Utopia Ray Victory", all "Chaos Numbers" summoned through Rank-Up having glowing Barian energy lines running through their bodies.
Story
When "Number" holders have a high level of a certain emotion, "Chaos Numbers" start to appear. For example, Astral and Yuma Tsukumo obtained "Number C39: Utopia Ray" when Astral was happy to know Yuma considered him a friend. Reginald Kastle obtained "Number C32: Shark Drake Veiss" when his desire for revenge, brought on by "Number 32: Shark Drake", overpowered him. Later, Yuma obtained "Number C39: Utopia Ray V" after Vector (as "Ray Shadows") gave Yuma "Rank-Up-Magic Limited Barian's Force" and their "friendship" was strengthened as a result, though this was used by Vector to get closer to Yuma. Later still, Yuma and Astral obtained "Number C39: Utopia Ray Victory" when their friendship was strengthened as a result of Yuma rescuing Astral from his own darkness.
When Summoned without the use of a "Rank-Up-Magic" card, they have the same ATK and DEF as their non-Chaos counterparts. When one is Summoned, the "Number" reverts to its neutral form and enters the Overlay Network. The Overlay Network then explodes, revealing the new neutral form, which then unfolds into the Chaos Number.
In Yu-Gi-Oh! ZEXAL II, Barians Summon "Chaos Numbers" through the use of "Rank-Up-Magic" cards. As implied, the "Chaos Number" Summoned this way is 1 Rank greater than its original form. Also, unlike their non-Barian counterparts, these "Chaos Numbers" have increased ATK and DEF. "Chaos Numbers" Summoned this way have a blood-red aura surrounding them, slightly resembling electricity and glowing Barian energy lines surrounding their bodies. When someone Summons a "Chaos Number" by Ranking-Up, they enter a contract with it in order to maintain control of it, at the risk of depleting their life, such as with Girag when he Summoned his "Number C106: Giant Red Hand". It can also put the user at risk in case the "Chaos Number" is destroyed, which can leave them severely injured, even to the brink of death. If a "Chaos Number" monster is Summoned via a "Rank-Up-Magic" card (except "Numeron Force", "Astral Force" and "Argent Chaos Force"), "Chaos Field" or "Don Thousand's Throne", their Overlay Units take the form of red diamond-shaped crystals as opposed to glowing orbs, and are referred to as "Chaos Overlay Units", just as with the "CXyz" monsters. The sealed "Barian Gate" appears while doing so.
"Number C" monsters have powerful effects, though this is balanced out by their requirements - needing 1000 or less Life Points for the "Number C" monsters that have the same Rank as their "Number" counterparts, or requiring specific monsters to be attached to them as Overlay Units (or in the Graveyard in the case of Number C101 and Number C103) for Ranked-Up "Number C" monsters.
Chaos Numbers
So far, 21 "Number C" are known to exist, as well as an additional 7 which are "Number C10X". Of these Numbers, two did not appear in the anime, Numbers C62 and C79.
| Symbol | Monster | Base Number | Neutral form | Owner(s) | Number location |
|---|---|---|---|---|---|
 |
Numeron Chaos Gate Sunya | Numeron Gate Ekam | None | Don Thousand (Originally) Nash Yuma Tsukumo Astral |
Right Horn |
 |
Chaos Chimera Dragon | Doom Chimera Dragon | None | Vector (Originally) Don Thousand Nash Yuma Tsukumo Astral |
Right wing |
 |
Chronomaly Chaos Atlandis | Chronomaly Atlandis |  |
Trey (Originally) Mizar Don Thousand Nash Yuma Tsukumo Astral |
Chest ring |
 |
Chaos Dyson Sphere | Dyson Sphere | None | Quinton (Originally) Mizar Don Thousand Nash Yuma Tsukumo Astral |
Two panels in the center sphere |
 |
Gimmick Puppet Giant Hunter | Gimmick Puppet Giant Grinder |  |
Quattro (Originally) Nash Yuma Tsukumo Astral |
Center of forehead |
 |
Shark Drake Veiss | Shark Drake |  |
Reginald Kastle/Nash (Originally) Yuma Tsukumo Astral |
Left side of chest |
| Shark Drake LeVeiss | None | Astral | Left side of chest | ||
 |
Utopia Ray | Utopia |  |
Yuma Tsukumo Astral |
Joint plate on left wing |
|
Utopia Ray V |  |
Yuma Tsukumo (originally) Astral |
Left shoulder | |
 |
Utopia Ray Victory | None | Yuma Tsukumo (originally) Astral |
Left shoulder plate | |
 |
Gimmick Puppet of Dark Strings | Gimmick Puppet of Strings | None | Quattro (Originally) Nash Yuma Tsukumo Astral |
Left wing |
 |
High Manipulator of Chaos | Manipulator of Souls | None | Vector (Originally) Don Thousand Nash Yuma Tsukumo Astral |
Right side of waist |
 |
Neo Galaxy-Eyes Prime Photon Dragon | Galaxy-Eyes Prime Photon Dragon | None | Astral | Left thigh |
 |
King Overfiend | Djinn Buster |  |
Number 96 (Originally) Vector Don Thousand Nash Yuma Tsukumo Astral |
Right side of waist |
 |
Heraldry Crest of Horror | Heraldry Crest | None | Number 96 (Originally) Vector Don Thousand Nash Yuma Tsukumo Astral |
Left horn |
 |
Abyss Supra Splash | Abyss Splash | None | Nash (Originally) Yuma Tsukumo Astral |
Middle panel of armour |
 |
Battlin' Boxer General Kaiser | Battlin' Boxer Nova Kaiser | None | Astral | Left Torso |
 |
Requiem in Berserk | Rhapsody in Berserk |  |
Alito (Originally) Vector Don Thousand Nash Yuma Tsukumo Astral |
Right shoulder plate |
 |
Gimmick Puppet Disaster Leo | Gimmick Puppet of Leo | None | Quattro (Originally) Nash Yuma Tsukumo Astral |
Top of right foreleg |
 |
Heart-eartH Chaos Dragon | Heart-eartH Dragon | None | Number 96 (Originally) Vector Don Thousand Nash Yuma Tsukumo Astral |
Right side of abdomen |
 |
Dark Storm | Dark Mist |  |
Number 96 (Originally) Vector Don Thousand Nash Yuma Tsukumo Astral |
Right horn on midsection |
 |
Numerounius | None | Unknown | Don Thousand (Originally) Nash |
Right thigh |
Chaos imaginary Numbers
While "Chaos Numbers" are generally Summoned by performing Chaos Xyz Evolution on a 'regular' (non-Chaos) "Number", there was a single instance where Don Thousand performed a form of Chaos Xyz Evolution on a monster that was already a "Chaos Number", creating what he called a "Chaos imaginary Number", referencing the mathematical concept of imaginary numbers. Technically, due to this card's name, it is not a true member of the "Number C" archetype.
| Symbol | Monster | Neutral form | Owner(s) | Base Number | Number location |
|---|---|---|---|---|---|
 |
Numerounius Numerounia | None | Don Thousand (Originally) Nash |
Numerounius | Right side of the head |
Trivia
- Of the "Number C" monsters that were released to the OCG/TCG, several do not mention their base "Number" form in their effects. This is because:
- One lacks a base form entirely - "Number C1000: Numerounius".
- The base form was released afterwards, such as "Number 5: Doom Chimera Dragon" after "Number C5: Chaos Chimera Dragon".
- The base form was released beforehand but had limited distribution, such as "Number 15: Gimmick Puppet Giant Grinder" and "Number 106: Giant Hand" debuting in the OCG as magazine promotional cards.