Greed Island! The game that Jin and his friends made and eventually induced Gon to go play. It is a rather rare game that is no longer published. In a tape left by Jin to Gon, he explained Greed Island and Gon thought that perhaps the clues to finding his father lied in the game itself.
Thus, Killua and him actively searched for the game, at first attempting to buy it (which was impossible, since the game had many high bidders, such as the millionaire Mr. Battera; he was intent on getting the game), however, they later switched to passing a test to be a player in the game instead.
Before you enter the game, you are given a memory card, then, you use your nen to enter the game. However, as Shalnark deduced, just hatsu is not enough to allow a person to leave the real world and enter a virtual one (in order to do this, a person's body and soul must separate, but hatsu alone cannot do this), thus, it is only enough to teleport a person from one part of the world to another. So, in reality, they are on an island in reality.
When you enter the game, you are told about the game: When you enter the game, you have a binder to store all the cards collected in the game. The binder has 100 slots in the beginning (#000 to 099) to store imposed slot cards (cards that have a number on them are placed correspondingly in the binder) and 45 free slots to store other cards. The main condition on ending the game is to fill up the imposed slots.
There are two spells you can use while in possession of the ring:
"Book" ---- causes the binder to appear
"Gain" ---- changes a card into an object to use
Cards can be collected when you find an object, such as a sword. Upon taking the object, it will immediately turn into a card that can be put into the binder. Objects turned into cards cannot be used as weapons. If you want to use the object, use "gain".
Also, if you obtain an object and you turn it into a card and later turn the card back to an object, the object cannot be turned again into a card. In other words, an item cannot be turned into a card twice.
Other than this, objects cannot be transformed into cards if: +++ The card number limit is reached. For example, though there may be many of the same objects available in Greed Island, only 3 of the objects can be changed into cards because that is the card's number limit. In other words, only 3 of the objects can be in card state at a time. More, and the objects cannot be transformed. Thus, you will have to wait for someone to say "gain" and turn their card into an object. Once someone changes one of those cards back to an object, you can transform the same object (yours) into a card.
Cards must be stored in the binder, or else they will turn back into an object after 1 minute. As with the earlier condition of not being able to have an object in card state twice, the object cannot be transformed back.
The card's difficulty to be found is indicated by a letter : S A B C D E F G H. S being the hardest to find and H being the easiest. The letter is followed by a number, indicating the amount of cards in circulation at the moment.
The lower the number, the rarer the card is. Also, if a person acquires an object, but the card number limit is reached, the object cannot be converted into a card. For example: suppose a card's limit is 4 cards and there are already 4 people in the game who own the card, then the next person who acquires the object corresponding to the card cannot change the object into a card.
Finally, if a person dies in the game, the ring and all their card data will disappear.
There are many spell cards in the game, such as those for attack/defense. However, no spell exists to kill or maim. Here are some of the spell cards considered "important":