Atop Mt. Coronets, after doing battle with Team Galactic grunts, Admins and the Team Galactic Boss, Dialga or Palkia depending on your version will have been awakened. After the legendarey trio appear, Dialga/Palkia's Powers will be qwelled but you are capable of fighting it. This is straight after the battle with the Team Galactic Boss, but luckily you can go back and heal. It is at Lv. 47

After battling and qwelling Dialga or Palkia, the three legendary Pokémon will be scattered around Sinnoh. Positioned in Lake Acuity is the Yellow Pokémon in the trio, Uxie. You battle him here but he is only here once so be sure to save. It is at Lv. 50

After battling and qwelling Dialga or Palkia, the three legendary Pokémon will be scattered around Sinnoh. Positioned in Lake Valor is the Blue Pokémon in the trio, Azelf. You battle him here but he is only here once so be sure to save. It is at Lv. 50

After battling and qwelling Dialga or Palkia, the three legendary Pokémon will be scattered around Sinnoh. Positioned in Lake Verity is the Pink Pokémon in the trio, Mesprit. Once you go to battle him, he runs off. This time his location is not registered in your Pokédex but rather in the Map in your Pokétch. He will appear randomly in the grass. It is at Lv. 50

Once you have obtained the National Dex and gone to the Island in the North East, you will encounter a fair few Pokémon not normally native to Sinnoh. However when you get to Stark Mountain, you team up with a trainer while going through the Mountain. Once you reach the end, she will take the item and go. Return to the Survival Area and she will be in one of the houses. Talk to her and she leaves. Return to the Mountain and Heatran will be there. You can only battle him once and he is at Lv. 70 so save beforehand

Regigigas, the leader of the Regis that was said to pull the continents together. Regigigas resides in the temple just north of Snowpoint City, deep in the ruins, he is asleep...until you transfer Regirock, Regice and Registeel over from your past games. With the three Pokémon in your team, you will be able to awaken Regigigas. Be warned as he is a very powerful Pokémon at Lv. 70. Try to incapacitate him but not faint him within the first few turns

After obtaining the National Dex, a new lake with the Turnback Cave by it. It is positioned just east of Route 214. In it is a maze like area with pointers telling you where to go. After finding your way through, you should find Giratina. This is the 3rd legendary Dragon to go with Dialga and Palkia. Once again you can only battle it here and it is at Lv. 70. With a variety of resistences due to both of its types, you best be prepared

After obtaining the National Dex, when you talk to the family in the house above the Sailor by the boat in Canalave Town, you will be told of Full Moon Island. Talk to the Sailor and he will take you there. The only thing on this island is Cresselia. Talk to it and it will fly off. Like Mesprit, it's current location will display on your Pokétch so you will have to trap it through that. It is Lv. 50 so be prepared

Manaphy, the Prince of the Sea, is obtained via a Special Event that was available for Pokémon Ranger. You can transfer Manaphy over to your game. The Egg it is in hatches after a while into a Lv. 1 Manaphy. However this Manaphy is able to breed and when you breed it, it will hatch into the Psuedo-Manaphy; Phione. A Weaker version of Manaphy

Once you obtain the item Membership Pass at the event, Go to Canalave City and you will be able to access the Motel which has previously been locked. Go there for a night's sleep and you will be disturbed by Darkrai in your sleep. When you wake up, a Diary will be there which contains Darkrai's location. Go to the Sailor at the bottom of the city and he will take you there. When you get to the island, you can go up and battle Darkrai. It is at Lv. 40

After you go to the event that is giving away Shaymin, you will receive the item called: Oak's Letter. With this item in your bag, go to the White Rock in Route 224. You will notice that the Route has been extended. Now as an extra long route, the Flower Paradise, all the way to the top right of the map, you must travel it all the way. At the end, in a flower filled field, you will find Shaymin awaiting you. It is at Lv. 30

Once you go to the event, you will receive the item called: Azure Flute. With this item in your bag, go to the Spear Pillar in Mt. Coronet where you battled Dialga or Palkia. Go to the symbol between the pillars and use the Heaven's Pipe. Some stairs will appear that will go up to the Hall of Origin. Here Arceus resides. Be warned as it is the highest level Wild Pokémon at Lv. 80 so be prepared