Mega Man Battle Network 4 Red Sun Cheats

There is a large hole surrounded by purple slime on a platform in Ura Internet area 6. In order to approach it, you need the chips ''Bug Charge'', ''Muramasa Blade'', ''Black Wing'', ''Element Dark'' and ''Poison Anubis''. Once you get close enough, it will suck you down to the secret dungeon, Black Earth.

One more thing to add:

To fight Duo SP, you need to have all the 7 symbols

1 for Duo
1 for Soul Complete
1 for Standard library complete
1 for Mega Library Complete
1 for Giga Library Complete
1 for P.A. Complete
1 for Forte SP

Go back to where Duo was and fight him there!

After completing the Black Earth dungeon, exit (plug out) and re-enter. You can now encounter Forte SP in Black Earth area 2, and obtain Black Barrier from him.

To get past the gate in Ura Internet area 5, you need all 150 regular chips. Once you get past it, you can fight the secret boss, Forte, and get his chip, Forte.

In multiplayer, Dark users are very tough because they become the Darksoul when you reduce them to 0 hp. However, if you use a chip or PA that freezes time and deals many hits, you can kill them without allowing them to become the Darksoul. A great example is the Pile Driver PA. Hope this helps you take out those cheap Darkies!