It differs from Monster Rancher 1 and Monster Rancher 2,because they were the RPG/Monster Breeding,this one is RPG/Adventure.It was also the first monster rancher game that you would not use via CD's to import monsters,therefore being for the Gameboy Color.
In the beginning, you must choose a male or female character (Alf or Aya) and take a quiz. The answers will determine which team of three monster cards you shall recieve- the Power, Miracle, or Speed team. The object of the game henceforth is to battle your way through various temples to earn more Attack cards and Item/Effect cards. If you defeat the boss at the end of each temple, you recieve a disk to unlock at the Shrine back in town to recieve a new Monster card.
In battle, there will always be 3 monster cards on each side, and you are allowed 50 cards in your deck. The object of the battle is to defeat all of your enemy's monster cards before the enemy can defeat yours. Each monster card has different HP, depending on the monster. Attack cards are powered by Guts- the more powerful the attack, the more Guts it uses. In each turn you must have 5 cards in your hand. The more cards you discard at the end of the turn, the more Guts you will recieve for the next turn. Defense cards exist, in which your monster softens the attack power of the opponent's move, or dodges it completely. Item cards can make attacks more powerful, restore life, etc. Since you are allowed only 50 cards in your deck, you must choose Attack/Defense cards for each monster evenly, and Item and Effect cards wisely.
As you progress through the game, you can increase your Breeder level, making more cards and Temples available. At the league, you can wager cards in battle- the more rare the card you wager, the better your prize will be. In certain areas you can also trade items for cards- the more rare the item, the better the card. You will want to obtain as many different types of cards you can, and progressively make your deck better and better.
At some point in the game you can combine monster cards- for example, if you combined a Suezo and a Dino to make Melon Suezo, the new Melon Suezo could use both Suezo and Dino Attack cards.
The basic monster cards you can obtain are as follows:
Golem- Absurdly powerful monster with incredibly powerful attacks, which use up a lot of Guts.
Pixie- Fairly weak attacks, but have excellent effects such as depleting foe's Guts, attacking all monsters, cannot dodge, etc. Also, the fact that Pixie hovers makes her able to dodge certain attacks.
Naga- Powerful monster with many specialty attacks.
Tiger- An all-around monster who has the ability to combine some attacks.
Gali- Fairly weak attacks but with useful effects.
Suezo- Suezo is the master of attacks that sap enemy's Guts.
Hare- Has powerful attacks but can backfire if dodged.
Dino- Like Hare, its attacks are powerful, but risky.
Mocchi- Very weak attacks, but with various effects.
Trivia: This game's translation from Japanese to English is notoriously bad, worsened by the limited amount of words than can fit on the GB's small screen. This game can be very difficult to understand at times.