Gameplay takes a drastic turn in Monster Rancher 4. It is the first game to have a preset monster as your first monster, being Garu. Monsters can now be raised in groups of up to five, and training is limited to what training items you have installed. It is also the first game to have a story that is present throughout the entire game.
The story is narated (partially) by the assistant Rio. She starts the story by introducing Phayne, the first main character in the series that isn't just assumed to be the player. Phayne had been stowed away in a ferry ship with a single Saucer Stone in his pack, hoping to become a Monster Breeder when the ship made port.
Some breeds are new to this game. There are 34 main types of monsters, but two different monsters can be combined together to create subspecies, thus making 328 different species available.
Here are the monster types: