Class Cards (クラスカード, Kurasu Kādo?), also called Servant Cards (サーヴァントカード, Sāvanto Kādo?), are artifacts created for the Ainsworth Holy Grail War, a system of summoning Heroic Spirits similar to Servants. Differing from allowing a Heroic Spirit to manifest, the cards encapsulate the Heroic Spirits, used by the participants of the Holy Grail War to fight amongst each other.
Much like the Servant system, seven cards are summoned during each Holy Grail War, corresponding to one of seven classes. The cards have a portion of the Heroic Spirits' power sealed inside them, and it can be said that they are the Heroic Spirits themselves. They draw out the power of Heroic Spirits, allowing either a Mystic Code or the user's own body to act as a medium for the Heroic Spirit's power. Overwritten by a fraction of the Heroic Spirit's power, they are able to fight others with that power. Meant to be utilized in the Ainsworth Holy Grail War, the Mage's Association of Illya's world is unable to analyze them in any manner.
One part of the process of creating the Class Cards robs the Heroic Spirits of their reason and pollutes their egos by passing through the Ainsworth's "box". Only the Gilgamesh Archer Card shows the ability to retain its ego without being polluted, allowing Gilgamesh's personality to overwrite the user.
The participants of the Holy Grail War and possessors of the Kaleidostick utilize the power of the cards with two methods. With the Include: Limit Expand (限定展開, Gentei Tenkai?) method, it temporarily materializes the weapon or Noble Phantasm of the hero by overwriting a Mystic Code until the Card is Unincluded. The true purpose of the Cards is to temporarily become a hero by accessing their full abilities. Install: Phantasm Summon (夢幻召喚, Mugen Shōkan?) grants the Noble Phantasm, Skills, and appearance of the Heroic Spirit. The user obtains a "fraction of their power", their own existence "overwritten" by that of a hero's existence. There is also Kaleid Install (カレイドインストール, Kareido Insutōru?), both Kaleidostick wielders using a single card together, utilizing the weapons of a Servant.
Unique to the Berserker Class Cards, Installing Berserker and then Installing another card, called Berserker Class Inheritance (バーサーカークラス継承, Bāsākākurasu Keishō?), confers the properties of Berserker to that Card's Heroic Spirit.
The Assassin Class Card is unique in that it is not linked to a specific Heroic Spirit. Much like the Fuyuki Holy Grail War, the Assassin summoned is always Hassan-i-Sabbah, but it picks one of the nineteen depending on compatibility with the Card User. One Class Card can manifest multiple different Assassins if used by other Card Users.
The Cards possess the ability to manifest as blackened Servants by being left to gather magical energy from the land. They possess no reason, and they possess a deteriorated, blackened appearance. The Heroic Spirits form around their Class Cards, utilizing them as their heart. Compared to their Servant counterparts, the blackened Class Cards have several "errors" from being stained, such as Noble Phantasms and Skills being ranked down. Their parameters are generally decreased by one or two ranks, varying from card to card. They possess fighting instincts and skill, but they are much weaker than their normal selves due to being like "phenomena without their own will." 
Known Class CardsEdit
|War||Servant Card||Identity||Card User|
|5th||Archer||Gilgamesh||Angelica Ainsworth (Doll)|
|5th||Archer (Second)||EMIYA||Shirou Emiya|
|5th||Saber||King Arthur||Zachary Ainsworth (Doll)|
|5th||Lancer||Cú Chulainn||Kayneth El-Melloi Archibald (Doll)|
|5th||Rider||Medusa||Kariya Matou (Doll)|
|5th||Caster||Medea||Atrum Galliasta (Doll)|
|5th||Assassin||Hassan-i-Sabbah||Shinji Matou (Doll)|
|5th||Berserker||Heracles||Beatrice Flowerchild (Doll)|
|6th||Assassin||Hassan of the Hundred Faces||Illyasviel von Einzbern|
|6th||Assassin||Hassan of Serenity||Miyu Edelfelt|
|6th||Berserker||Lancelot||Sakura Matou (Doll)|
|6th||Apneic Beauty Class Card||Unknown||Darius Ainsworth|
|6th||Authoritarian Personalism Class Card||Unknown||Darius Ainsworth|
|6th||Unnamed Dagger Class Card||Unknown||Darius Ainsworth|
|6th||Ninth Prayer Class Card||Unknown||Darius Ainsworth|
|6th||Crown Undertaker Class Card||Unknown||Darius Ainsworth|
|None||Nameless Class Cards||None||Ainsworth Family|
- ↑ PRISMA material/pre
- ↑ Hiroshi Hiroyama Blog 11/27/10:
Q:So Ciel (and the other charas) can fight Arc in MB because Arc's holding back and fighting game conventions. It seems [Ciel] is overwhelmingly strong compared to even Mabo back when he was an active agent, so without her immortality/NP Bazett would probably lose. So the question I've been having is, for the cards that have been shown, how much power of the original Servants are they drawing out when they materialise?
A: Well, Arc is a monster who's probably in the world top 3 when she gets serious... As for blackened servants coming from the cards, it varies but it's OK to assume they get 1 to 2 rank drops in stats compared to their original portrayals. Also, they have fighting instincts and skills, but since they're like phenomena without their own will, they're probably much weaker than the originals shown in their respective works. Like, with Bazett vs Lancer, he wouldn't even get a chance to use Gae Bolg before he's beat up.