Mewthree
Super Cheats provides the answer for how to get Mewthree, a very rare, powerful Pokemon. Be forewarned that it will not be easy to catch Mewthree, as its power level is at 100 when you find it. In Cerulean Cave, you will find a man who will ask you a series of questions. Give him the answers "Yes," "No," "No," "Yes" and your name. He will laugh at you, and the next wild Pokemon you encounter will be Mewthree.
Mewthree Eggs
There is one other way to obtain Mewthree, and that is through producing baby Mewthrees. According to Super Cheats, to do so, you must put Mew and Mewtwo together in your nursery. The eggs they produce will hatch with Mewthree in them. This is a much easier way to get Mewthree, as it will be a less powerful Pokemon, not being wild and being young instead.
Dragonite
One difficult Pokemon to obtain in Chaos Black is Dragonite. To do so, you must get and purify all shadow Pokemon. You must then go to the top of the lighthouse in Gaton Port, where someone will have a shadow Dragonite.
Similarities to Ruby
If you possess Pokemon Ruby, the gameplay is similar to that authentic Pokemon game, so many of the same hints from the game apply to Pokemon Chaos Black. As an example, according to IGN, you begin by speaking with Professor Birch, who gives you basic instructions in catching and keeping Pokemon. Next, go to Littleroot Town, then back to Professor Birch's. You will receive guidance from his wife there.
Cheats and Codes
The master code is as follows: 72BC6DFB E9CA5465 + A47FB2DC 1AF3CA86. Some obstacles, according to Cheats Guru, require the "walk on walls" code: 509197D3 542975F4 + 78DA95DF 44018CB4.