Number C " Number C " , short for " Chaos Number " ( " Kaosu Nanbāzu " ) , is a sub - archetype to both the " C " , " Chaos " and " Number " archetypes . They are evolved forms of the base " Number " , which are Summoned by overlaying their base counterpart through Chaos Xyz Evolution . They are used by Yuma Tsukumo , Reginald Kastle / Nash , Mizar , Girag , Alito , Vector , Number 96 , Quattro , Rio Kastle / Marin , Dumon , Trey , Quinton and Don Thousand in the " Yu - Gi - Oh ! ZEXAL " anime and " Yu - Gi - Oh ! D Team ZEXAL " manga . They are support ed by the " Rank - Up - Magic " archetype and " Chaos Field " . 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 " 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 " " , all " Chaos Numbers " summoned through Rank - Up having glowing Barian energy lines running through their bodies . Story . When " Number " holder s have a high level of a certain emotion , " Chaos Numbers " start to appear . For example , Astral and Yuma Tsukumo obtained " " when Astral was happy to know Yuma considered him a friend . Reginald Kastle obtained " " when his desire for revenge , brought on by " " , overpowered him . Later , Yuma obtained " " 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 " " 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 " , Barian s 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 " " . It can also put the user at risk in case the " Chaos Number " is destroy ed , 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 attach ed to them as Overlay Units ( or in the Graveyard in the case of and ) for Ranked - Up " Number C " monsters . Chaos Numbers . So far , 18 " Number C " are known to exist , as well as an additional seven which are " Number C10X " . 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 . Technically , due to this card ' s name , it is not a true member of the " Number C " archetype .