Digimon World 4 (known as Digimon World X in Japan) is the second Digimon video game on PlayStation 2, GameCube and Xbox game consoles simultaneously. Instead of being a standard RPG like the previous Digimon games, Digimon World 4 has hack and slash gameplay and supports up to four players. The game offers a choice of one of four starter Digimon: Dorumon, Veemon, Guilmon, and Agumon. They are each new members of the "D.S.G. (Digital Security Guard)." Based on Digital Monster X-Evolution, it is immediately revealed that a computer virus known as the "X-virus" is spreading quickly and is infecting many Digimon. "The Yamato Server" has disappeared, and a new server known as "The Doom Server" has taken its place. When the first few sections of Level 1 are completed the player finds out that The Doom Server may in fact be The Yamato Server. The player is then sent to destroy the "Doom Dome." This is where the first real boss appears, Apokarimon. There is no difference between each game system, except for the graphics.

Unlockables

Black War Greymon X
Clear (wormhole) dungeon IN HARD MODE

Imperial dramon Paladin Mode
Finish the FINAL SIDE-QUEST (Worm Hole Dungeon) in V. Hard Mode with any Digimon.

Ultimate and Mega Level Digimon
Follow the instructions given, Note: Play in normal mode

Clavisangemon - Complete Undead Yard with Veemon

Clavisangemon (second way) - Complete Item Road with Dorumon

Herculeskabuterimon - Complete Undead Yard with Guilmon

Herculeskabuterimon (second way) - Complete Item Road with Agumon

Wargreymon - Complete Undead Yard with Agumon

Wargreymon (second way) - Complete Item Road with Guilmon

Weregarurumon Complete Undead Yard with Dorumon

Weregarurumon (second way) Complete Item Road with Veemon

Unlockable Modes and MP Techniques
This can be done while playing either alone (single player) or multiplayer (more than one person). But in order for the mode's to be unlocked in multiplayer, you have to switch your players to the first slot.

Hard Mode - Complete Normal Mode Once (Applies to first player only, to unlock for other players, swith them to the first slot.)

Super Hard Mode - Complete Hard Mode Once (Applies to first player only, to unlock for other players, swith them to the first slot.)

Secrets

Unlimited Bits and items
This trick requires your main digimon as player one and any Digimon as player two. Give all your Bits to player two. Then, save player two at the save keeper. Next, have player two give all Bits to player one. After that, have player two quit the game at the save keeper, but this time without saving. Then go to the Call Keeper and have player two join in again with the same Digimon. Repeat this from the beginning until you have 9,999,999 bits, both in the bank and pocket. Note: You can also use this trick to duplicate items. This is very useful if you want to give some rare weapons and armor to a friend.

Here's one of the toughest boss battles in the game: