Tetra Master is the card game in FF9. Some people call it Quad Mist, but its official name is Tetra Master. ALl over the world of FF9 if you talk to someone using square, they'll play you in this game. Some are better then others, some have better cards then others, but you'll never find out unless you challenge them.
If you don't know how to play the game, then here's a comprehensive guide to how to be a master of Tetra Master. Having to know how to play Tetra Master is essential to the game, since you cannot beat the game if you don't become a finalist in the Treno Card Tournament.

Achieving Cards
Finding crds can be easy and sometimes rather tough. One way is to win cards from opponents. This is one of the easiest ways, if you're good at the game. The second is beating monsters. When you kill monsters in battle sometimes they leave their card behind, or sometimes leave another monster's card. That's probably the easiest way. The hardest, yet most rewarding, if finding them in treasure chest or recieving them for completed tasks.

Card Basics
Well, i have the toughest job here! It's probably much harder to describe the game then it is to play! First, you must get 5 cards. Win a few from monsters or buy some at Treno, and start your game. Choose 5 cards (or just pick the 5 you have). Pick wisely, look for the number of arrows and how they are arranged, and the 4 numbers/letters on the lower middle of the card. I'll explain why that's important later. After ghetting your cards together a 4x4 playing board appears. Sometimes some spaces are blocked off to make the game interesting. I've never seen more then 6 be blocked. If you've seen more contact me at TripleTriadId, and then I'll change this puppy. After the blocking of the spaces is done, a coin toss will day who goes first. If it'sd a blue looking you, you go first. If it's a yellow or orange looking coine, the opponent goes first. Now you're off!

Card Statistics The first number on the card is the attack power. This is in hexadecimal, from 0 to E, and E is one helluva ass whoopin against the opponent.
The second stat is the card's attack type. P is phsyical, M is magical, and X attacks the lowest defense on the other card (Pretty nifty, no?), and an A attacks the lowest number on the card (Hot doggy!).
The third stat represents the card's phsyical defense (or the number attacked by P) and the fourth represents the magical defense (or the number attacked by M). Each of them are in hexadecimal like its attack power (Imagine an EAEE card? Whoa!)
When two cards battle, the newly-placed card uses it's attack power and attack type. So if it has an A in attack and an M in type, it would use it's A (or 10 translated from hex) against the opponent's magical defense. If they opponent had an E in phsyicalk and a 4 in magical, it will most likely lose. If if was close, like it had a 9 in the magic defense place, there's a small chance it might come out victorious.
If you play with the same cards tons of times, there's a chace it's stats will go up, so play them cards trillions of times and get your five cards to EAEE and be unstoppable!
Also, the arrows represent which way it can attack other cards. So if you have an arrow on your right side, and it is placed to the opponent's adjacent left, and the opponent's card doesn't have an arrow there, it'll take that card. If it does have an arrow there, then that's when battle occurs. Also, if you win a battle, you can do a great thing called combo. If you remember Triple Triad's combo rule, then you might think this is similar. If you in a battle, and your opponent's card can take any other cards around it by having arrows meet no arrows then it'll take even more cards. You can end up taking all of your opponents cards (if you play right) in one move!

Card Inventory
If you go to the main menu on your FF9 game and select "Card", then you can view all of your cards, your collector's level (which will be explained later), your toal of wins, your total of losses, and your total of ties. My tip is to discard weaker cards (like low stats and few arrows) so you can have room for rare cards. This is because you can only hold 100 cards at a time. Try and get all 100, you can only hold one of each, but your collector's level will be through the roof.

Rare Cards
These babys are the ones you want. They are usually quite strong and can beat most of the other cards. Some cards are so rare you only have the chance to get hem once, and if you screw up it's all over. Ways to get rare cards are:
1) Find them in treasure chests. You get some great cards this way, but this is not the most rewarding
2) Beat extremely good players. This is probably the most rewarding. Beating the card ghosts in Memoria is the best place to find great cards.
3) Find cards in Chocograph treasures and with Dead Peppers. This is one of the most rewarding too. You can find some good cards in these, so don't pass up the chance to snoop around with Boco!

Collector's Rank
Here's something that's hard to figure out, but when you do it's quite simple. Your collectors rank starts at 0, and goes all the way up to 1700. This number measures your prestige as a card player. The more unique cards you have, the higher your rank. Also, each card must have a unique arrow arangement, AND you gotta play every card enough to have them all at attack level A to get a collector's level of 1700.