Never watched Card Captor Sakura? Confused by the Clow Cards? Planning a match involving Sakura or Shaoran and searching for ideas? This may help.
A cheerful, energetic, good-natured girl, Sakura had the job of Card Captor thrust upon her, but she performs with determination. She's not the brightest girl, but she's far from stupid, and she's proven to be a fairly creative and effective battle tactician in recapturing the Clow Cards. When she knows an opponent's capabilities and she has the opportunity to plan, Sakura often works out a reasonable approach. New developments during a fight, though, tend to startle her as much as anyone else.
Sakura isn't a trained fighter; however, she has incredible raw athletic talent, and often outperforms Shaoran in areas such as running and obstacle courses. Unlike many magical girls, Sakura possesses a good deal of grace and coordination. Combined with her athletic ability, that gives her a knack for dodging that will be as useful in Ultra as it is against the Clow Cards. It's a good thing, too, because Sakura is a ten year old; even with magical enhancement, a few solid blows would finish her. She's also not that strong physically -- though she is stronger than she looks, for what that's worth.
In the ring, Sakura is likely to emphasize mobility and distance attacks with her magic. If she gets in close by choice, it will usually be because she's under the influence of a card, such as Sword, Fight, or Power, which makes up for her physical shortcomings. She does have a strong will (very strong, considering her age), is reluctant to give up... and possesses great magical potential, enabling her to sense magic and to control the Clow Cards.
Shaoran is of the Li clan, a famous family of magicians descended from Clow Reed, creator of the Clow Cards, himself. It is Shaoran's belief that he should have been chosen as the Card Captor, and he becomes Sakura's rival (and reluctant partner) in recapturing the cards. He is intelligent and takes a pragmatic approach toward most things, which makes him come across as cold and unconcerned; the fact that he is self-confident to the point of arrogance (even if he *can* back up most of his boasts) doesn't help matters. He's not evil... but he's very focused on his chosen goals, and he doesn't care overmuch what others think of him, so long as he feels he's making progress toward it. In the same vein, he doesn't hurt or terrorize innocent bystanders, but he looks down upon people who would challenge him but who he thinks are "weak". (He mostly views Sakura, who's "challenged" his "rightful" status as Card Captor, this way.) Kero-chan calls him "the brat", and it's a pretty accurate label, most of the time.
Shaoran is a martial artist, trained in an unspecified Chinese martial art -- likely a form of kung fu. He's not a prodigy on the level of such Ultra fighters as Ranma or Iori, but he's good enough to fight to a draw people with training comparable to his but who enjoy the advantages of greater age (reach, strength, etc.) -- he's probably a match for early Shingo or Akane. He can fight unarmed, but often uses a sword; for typical Gamma/Lambda matches, it will be blunted, but he might use a sharp one under Hardcore rules. However, while he's much stronger in hand-to-hand than Sakura, and more durable, he still can't take as much damage as most of Ultra's fighters, and he's not quite as fast as Sakura is. He does have some magic of his own, which is detailed below.
In the ring, Shaoran will be cool and efficient. He's not above trash talking, especially if he's winning, but he's not stupid enough to get wrapped up in a speech and forget about his opponent. He has a bit of a showman attitude, enough to realize that a quick, one-sided match is boring, and boring is bad, and has told Sakura they need to refrain from doing anything that looks too unfair; in spite of that, he's shown a willingness to use questionable tactics at the end of a match for a cheap win, and he's not one to overlook an opponent's moment of distraction, or any other opening or advantage he could get. He isn't bothered if the audience boos him; he's decided that getting a reaction, any reaction, is their job, and this way he can get a reaction without creating too many artificial restrictions for himself. After all, it's just a show... the win is as entertaining for the audience whether they cheer or not, right? He won't aim to seriously harm or cripple his opponents, but he won't shed many tears if they get hurt, either... they were in the ring, they knew the risks, so it's not his concern...
Keroberos, usually known by the nickname "Kero-chan", is the Guardian Beast of the Seal, whose job it was to look after the Clow Cards. He was the one who bound the Clow Key to Sakura, making her the Card Captor, and now he serves as her advisor, general source of information on the cards, and companion. His appearance is that of a yellow plush lion/teddy bear with wings and a lion's tail. He speaks with an Osaka accent, and he's fond of food and video games. He's also rather narcissistic and self-promoting, but he really is fond of Sakura. He doesn't fight, naturally, but he'll usually be hanging around Sakura's corner during her matches, cheering her on.
Shaoran is descended from a clan of magicians, including the wizard who first created the Clow Cards. He lacks Sakura's sheer magical potential; however, unlike Sakura, Shaoran is trained in the use of that potential. Aside from the ability to sense magic in general and the Clow Cards in particular -- an ability Sakura shares -- he is able to create a variety of elemental effects. This magic is less powerful and usually much less flexible than that which is invoked through the elemental cards, but it has the advantage of drawing on Shaoran's own power, and not requiring an outside source.
Shaoran will usually focus and direct his elemental magic through either his sword or through paper wards (ofuda). It is unclear whether he can do so without one of these items. The effects he most often invokes are as follows:
WIND - "Petals of wind, hear my call!" This invocation creates a burst of gale-force wind. It affects a fairly narrow area and short range, and seems limited to exerting uni-directional force. The force exerted is fairly strong, easily capable of throwing a grown man off his feet; it could also cause some generalized battering damage to less durable fighters, though it's probably on the weak side as a projectile attack. Shaoran most often channels this through his sword, with the wind springing from the tip.
THUNDER - "God of thunder, answer my call!" This spell causes a miniature lightning bolt to leap from the tip of Shaoran's sword, or from the surface of one of his ofuda. While it's not as strong as the Thunder card's attack, it does pack a pretty strong punch. It seems to be one of his favorite attack forms; he's also used it as a "trap" by setting up two ofuda facing each other and invoking the spell when his enemy stepped between the two.
FIRE - Shaoran usually uses this spell in conjunction with his ofuda; he'll throw one of the wards, which will (hopefully) attach itself to his opponent and then burst into flames. He usually seems to use this more as a distraction or annoyance than as a damaging attack. That may simply be his own preference, or it may be that the spell's power is low. He's also used it as a convenient "candle" on at least one occasion, making it somewhat more flexible than his typical magic.
WATER - "Lord of the sea, hear my call!" This magic appeared in episode 78 (UltraReboot 4). It caused a torrent of water to spray from the tip of Shaoran's sword. Again, it lacks the flexibility of the Watery card, but it appears to exert a good deal of pressure, and serves as a reasonable projectile attack.
Shaoran may possess similar low-level control of other elements as well.
The Clow is a magical deck of cards named after Clow Reed, the wizard who created them. Each card is the true physical form of a type of spell, usually a natural effect such as The Windy or The Thunder. Some cards, such as The Mirror or The Erase, stray away from the natural, but Clow Reed appears to have lived in the late 1800s, and technological cards are almost entirely absent.
Each card has its own personality. Some are gentle and some are aggressive; some are defensive and some are offensive; some are relatively neutral, some are very obedient or very free-willed. All cards will obey the person who captured them and signed his or her name on them; however, their personality sometimes affects the manner in which they will obey. An aggressive card like The Watery might interpret a hasty or incomplete order in such a way as to cause the greatest damage, whereas a gentle card might not do so unless directly ordered to. Sakura's oldest card Windy will do exactly what she intends it to, while a newer, more aggressive card might instead do exactly what she tells it to... a subtle difference. This won't come into play every fight, or even terribly often, but it could make for a useful plot device.
In Ultra, Sakura probably carries 4-6 Clow Cards with her to any given fight. Shaoran, being more self-reliant (and possessing fewer cards) may carry only one, or even none at all.
How many of these cards can be used at once? Well, the canon answer, in the early half of the manga/anime (which roughly corresponds to Ultra Sakura's position) is: as many as she can spare some concentration for. In theory, she could use all of them; in practice, the most she's shown using at once is four or five. However, for Ultra purposes, I recommend not having Sakura use more than two cards at a time, and I'd be very careful even with that. It may help to think of the cards as similar to pokemon: they already give Sakura a lot of versatility compared to most Gamma-level fighters; using multiples at once on a regular basis might be too overwhelming. Again, what's good for the Ultra story is more important than what's in the canon of any one series.
One other thing that bears mentioning... as seen in episode #73, the spell of sealing that the Clow Key uses to capture the cards is apparently similar enough to the mechanism pokeballs use to catch pokemon that the Key can seal pokemon into cards. The exact details and ramifications of this have yet to be explored. It is unknown whether a pokeball could be used to capture a Clow Card.
What if you need a specific effect, but you don't see it listed below in the long section about "canonical" cards? Simple. Make one up. Remember, the needs of the Ultra story come before any individual series' continuity. A few guidelines to keep in mind:
Power level. Sakura and Shaoran are Gamma-level competitors. It's true that a few of the canonical cards could give pause to even Omega-level fighters... but it's also true that they wouldn't be making full use of those cards, if they use them at all. A "Destroy" card is probably going too far.
Theme. As was mentioned above, most of the cards are natural in origin, and none would be from the late 20th century. "The Computer" probably isn't a good choice for a Clow Card.
Narrowness of concept. The vast majority of the Clow Cards do one specific thing, and even those that do more are linked by a fairly tight concept, such as "controls water". A single card that makes grass grow, changes lead to gold, kills insects, and makes salad is probably too broad a concept.
The following is a pretty comprehensive list of the "canonical" Clow Cards, those which appear in the Card Captor Sakura manga and/or anime. They are broken down into cards which are definitely possessed in Ultra continuity, cards which are not definitely possessed in Ultra continuity but might be generally useful, and cards which are not definitely possessed in Ultra continuity and are probably not generally useful.
A star (*) by its name marks a card belonging to Shaoran.
A double minus (--) by its name marks a card that was possessed at one point in Ultra canon but was subsequently lost.
The following are Cards that Sakura and Shaoran are known to possess in Ultra continuity (they've been specifically mentioned in an Ultra episode):
WINDY - Sakura's first card, the Windy is extremely responsive to her desires. As one of the Element cards, it also commands a lot of power and versatility. Specifically, Sakura can use it to create or control wind. The wind can be quite forceful. Sakura also often uses Windy to bind and hinder an opponent.
FLY - When this card is invoked, a pair of large birdlike wings grows from the Clow Key staff. Sakura then rides the staff in flight. Sakura might use this if she feels a need for extra mobility, but it does make casting other spells difficult.
SHADOW - This card has the ability to control shadows in various ways. It can be used as an attack, to bind an opponent, to temporarily solidify a shadow, or even to cause a person's shadow to interact as though it was that person (so striking a person's shadow would be the same as hitting that person, for instance). However, a bright enough light will dispel the card's effects; it cannot create darkness, only gather existing shadows from the surrounding area.
WATERY - Another elemental card, this one offers creation and control of water in liquid form. It is an aggressive card by nature, so its attacks are more effective than Windy's, even though the two cards are at the same power level. Sakura tends to use Watery only as an attack.
JUMP - When invoked, this card manifests as a small wing-like aura around the user's ankles. It allows its user to make amazing leaps. Sakura has found it a useful mobility effect in Ultra, although most of her opponents could probably mimic its effects in that limited space through their own abilities.
ILLUSION - This card is used to cast an illusion. The image will take the form of something the viewer either desires to see, expects to see, or fears -- meaning, usually, each viewer will see a different image. Lack of control of the image makes this card less useful than it might sound, but it's still served Sakura as a distraction on occasion. In episode 70, Shaoran expressed some doubt as to whether its use would be legal in Ultra.
THUNDER - This card offers creation of electricity, usually in the form of a lightning bolt for attack purposes. Sakura might use it if she felt a projectile attack was warranted.
SWORD - The power of the Sword transmutes the Clow Key, shaping it into a long straight sword with a basket hilt. Its wielder gains the skills of an expert swordsman while the sword is held. The power of the sword depends on the will of the wielder -- it can be used simply to stun, or it can cut through solid stone, depending on what its wielder desires. This card helps Sakura in close combat, since she has no formal combat training.
* TIME - A powerful card that grants control over time. It can be sped up, slowed down, stopped, or reversed, and those in the area of effect who are not shielded won't realize what happened. Shaoran refrains from using the Time card to its complete potential for obvious reasons, but in episode 71, he used it to increase his personal time by a factor of five, becoming much faster than usual. In episode 73, Sakura used it in a desperate and successful attempt to escape Pikachu's attack.
ERASE - The power of this card can erase a target person or object from reality. It can also later restore them, unharmed. This card is not used against Ultra opponents, for obvious reasons. (It would certainly rate a "killed the opponent" disqualification anyway, even if it is reversible.)
MIRROR - The Mirror can create duplicates of a given person (often Sakura herself). Sakura likes to use this to create identical but insubstantial mirror images of herself to confuse opponents. The card could also create a physical duplicate of a person, but cannot duplicate any special knowledge that person may possess (such as martial arts techniques). Either way, the legality of this second use in Ultra is not established (it might count as outside interference).
FLOWER - Creates any type and quantity of flower. Good for impressive-looking entrances, and not much else, as far as Ultra is concerned. Sakura first used this card during her entrance in episode 73.
FIGHT - The Fight card, like the Sword, grants its user a high level of skill. In the case of Fight, however, the skill is with unarmed martial arts. As a side effect, it slightly enhances such physical attributes as striking power, stamina, and reflexes. Sakura first used this card in episode 76.
-- PIKA - Not a canon Clow Card, but once possessed in Ultra, this was actually the pokemon Pikachu sealed into the form of a card in episode 73. At the time, Sakura was unable to release him, and Shaoran took the card. In episode 76, Sakura was apparently able to release him in a fight, and Pikachu performed his thundershock attack. In episode 78, Ash stole the card from Shaoran and ultimately freed Pikachu by using a lightning stone to evolve him into Raichu. The evolution apparently broke the binding spell that had locked Pikachu in card form.
SHOT - Fires energy blasts that look like small glowing spheres at the target. The shots are less damaging than some of the other attack cards, and they have a relatively quick rate of fire, making this a potentially useful card in an Ultra fight. Sakura first used this card in episode 78.
ARROW - Fires a single arrow, which then splits into multiple blasts of energy. This is fairly similar to the Shot card, but more damaging. Sakura would probably prefer Shot, but Shaoran might advise her to use Arrow instead. Sakura first used this card (at Shaoran's recommendation) in episode 78.
The following Cards have not been specifically mentioned in an Ultra episode, but might be useful in Ultra:
WOOD - A gentle card that possesses the ability to make a tree grow very rapidly from nowhere. It also offers some control of living wood, such as moving tree branches to clear a path. Of limited usefulness in combat, but potential uses exist, especially in special setting gimmick matches.
RAIN - Can create rain in a small area -- anything from a gentle drizzle to a deluge. Typically not very useful in a fight. Shaoran might encourage Sakura to use it against a Jusenkyo-cursed opponent, to try to gain an advantage, though.
SILENT - Prevents a target from speaking or otherwise making noise for a short time. Sakura might find use for this against opponents like Tifa or Zell, who need to speak to use their magic.
SHIELD - This card likes to protect valuable things. It can be used to project a shield of force around a person or object to repel attacks; however, a great enough impact will break the shield. It can also shield against non-physical effects -- in the anime, Sakura used it to protect herself from the effects of the uncaptured Time card.
POWER - When invoked, this card grants incredible strength and endurance to its wielder. Sakura might find a use for it in Ultra; on the other hand, it doesn't increase skill at all. It would let her hit harder, but not with any more accuracy.
MOVE - This card enables the user to move small objects around without touching them. It's magical telekinesis, basically. It's not terribly useful directly against a living being, but it's a potential surprise.
* FREEZE - Creates ice. Might be semi-useful as an entangling attack, although it seems to take a while to completely freeze.
THROUGH - When invoked, this card enables the user to pass harmlessly through another physical object. Probably less useful than it seems, since the effect is fairly temporary and would need to be constantly re-invoked in order to avoid blows in a fight. Might have applications for a surprise or two, though.
BUBBLES - Can be used to create an abundance of soap bubbles. Mainly useful for cleaning, but the ability to make the ring slippery might come in handy, especially if Sakura is also carrying the Fly card in that particular fight.
The following Cards were not mentioned in an Ultra episode, and are probably not very useful in Ultra, being either too weak, too powerful, or with a purpose too unsuited to fighting in the ring. They are mostly self-explanatory, but listed for completeness:
MIST - Creates a cloud of magical mist that has the ability to weaken wooden structures -- the mist is corrosive in nature. More dangerous than it sounds, due to possible unforeseen collateral damage.
* STORM - Creates a tornado, and possibly other inclement weather conditions. Chances are Shaoran wouldn't try to use this one indoors...
FLOAT - Allows the target to float slowly through the air, like a balloon. Not nearly as fast or maneuverable as Fly, which would probably be preferred in Ultra.
GLOW - Creates one or more softly glowing lights, similar to fireflies. Not enough to blind someone; in most cases, it'd be a momentary distraction at best. It might be used to make a flashy entrance some time, though.
LOOP - Twists space in a small area so that it loops back on itself. People caught inside it will find themselves constantly going around in circles. In an area as small as the ring, this isn't as useful as it sounds, although with planning Sakura might be able to get an opponent to hit himself with his own projectile attack. People would soon catch on, but it could work once or twice.
SLEEP - Puts the targets to sleep. This is probably illegal in Ultra; even if it's not, the noise in the UltraDome would probably awaken the targets quite easily.
SONG - Duplicates the voice of the best singer in the area, and sings songs in that voice.
LITTLE - Causes the target to shrink.
MAZE - Transforms an area into a confusing maze. The maze cannot be circumvented by flying; its walls will rise to keep up. Pretty useless in the ring, though, since it's so confined... and in a fight outside the ring, it would be at best a delaying tactic. And probably would annoy the audience. Chances are Shaoran would recognize this and wouldn't let it be used.
* RETURN - It takes a great deal of concentration and energy, but Shaoran can use this card to return a person or object to their own past. Again, useless in a fight; it takes too much effort.
BIG - Causes the target to grow.
SNOW - Creates snow. A bit of a pain, indoors, but not much else.
VOICE - Mimics a voice. Might be good for a distraction, but its overall use is pretty limited.
CREATE - When invoked, this card creates a magical book. Anything that is written inside the book will come into being, but it will vanish again once the book is closed. Probably too powerful for Ultra.
* CHANGE - This card is used on two living creatures at the same time. It causes their minds to be switched into each other's bodies. It probably wouldn't be used in Ultra.
LOCK - Magically prevents an enclosure, such as a door or chest, from being opened. Might be useful in a steel cage match, though they'd have to be pretty confident of a KO...
* SAND - Creates (to an extent) and controls sand. Probably not too useful in the ring.
WAVE - Allows the user to manipulate water to create waves. Since the water must already be in existence, this card is completely useless in an ordinary Ultra match. In the rare cases where it might come in handy, Watery would do the job just as well, and provides more flexibility.
SWEET - Sweetens food or drink, or changes everyday fare into candy. Not really useful in the ring.
FIREY - The third elemental card, Firey allows the creation and control of flame. Like Watery, it is an aggressive card, used primarily for attacking. It is listed in this section because it's one of the last to be collected, and it's collected right before a major development in the series. If it's used in Ultra, be careful not to introduce major spoilers or increase the complexity of the characters' backstories too much.
DREAM - Seems to project dreams. Also allows the user to dream a prophetic dream. Might make for an interesting plot point, but it's not useful in a match.
EARTHY - The fourth of the elemental cards, Earthy allows control of earth and rock (but not of plants - that's Wood). It is suited to defense as well as attack, and is a gentle card compared to Firey or Watery. It is one of the last cards to be collected, and the notes on Firey also apply to Earthy.
DARK - Creates and controls darkness. Similar to Shadow in many ways, but with more power and fewer limitations; Dark is (along with Light) one of the two strongest cards in the deck, according to anime/manga canon. It's also one of the last to be collected, and since it's stated in Ultra that Sakura's deck is not yet complete, it would be safe enough to ignore this card and say that it hasn't been captured yet.
LIGHT - Creates and controls light. See the "DARK" note above.
TWINS - Creates a duplicate of the target. Most of the function of this card is already covered by Mirror.
The following cards exist in the anime, but I don't have certain knowledge of their effects. They are included for completeness. Look for them to be updated eventually. If you'd like to use one in Ultra, go ahead and define them whichever way you think would be more useful; there's no reason the Ultra-canon version couldn't have slightly different powers than the anime-canon version.
LIBRA - Allows the user to tell whether or not the target is telling the truth. If not, it apparently has the ability to "punish" the target in some way, but I'm not certain just how that works. Either way, it's probably not a terribly useful Card for Ultra.
* DASH - Increases the user's running speed. I'm not sure whether it increases overall speed and reaction time, which would be much more useful in Ultra.
CLOUD - Creates a cloud. This might or might not be useful as a technique to blind and disorient the opponent; I'm not sure how small it could be made.
This FAQ is up to date as of episode 77.
For more info on a particular canon Clow Card, check out The Complete Clow, the page from which I obtained explanatinos of the cards from the anime I hadn't personally encountered.
Spoiler info section coming soon.