POKEMON DIAMOND AND PEARL LEGENDARIES

#483 - Dialga and #484 - Palkia
    Depending on the version, Dialga or Palkia will appear on top of Mt. Coronet (Spear Pillar) while you face Cyrus. Contrary to some rumors, you do not directly go from the Cyrus battle to Dialga/Palkia. You do have time to save afterwards.

There is no way to catch Dialga in Pearl or Palkia in Diamond, but you can see it to add to your Sinnoh Dex. After seeing Azelf, Uxie, and Mesprit, you can go to Celestic Town and talk to Cynthia's grandmother. She'll show you a picture of the Pokemon.
#480 - Uxie, #481 - Mesprit and #482 - Azelf
       After you capture or defeat Dialga/Palkia at the Spear Pillar, you can revisit all of the lakes to find the Sinnoh trio. Each Pokemon waits in a cave in the middle of each lake. At Lake Acuity by Snowpoint City, you can find Uxie. Azelf is found in Lake Valor near Pastoria City. Mesprit can be located at Lake Verity near Twinleaf Town. Uxie and Azelf make it simple and just let you battle them, but Mesprit wants you chase it down first. Mesprit will appear in random routes afterwards.

One way to make catching Mesprit (and later, Cresselia) easier is to find a place where any route ends and another begins. Keep going back and forth between the routes checking the Marking Map as you go, and Mesprit will eventually end up where you are. This should make catching Mesprit much easier. Note, however, that the Pokemon can still flee the battle even if you put it to sleep.

After Obtaining the National Dex

#485 - Heatran
On your first visit inside Stark Mountain, you'll be accompanied by Buck. Once you get through the large room, he'll take the treasure, a Magma Stone, and leave. Exit and go to the Survival Area to talk to him in one of the houses. Apparently, the volcano has been acting up, so he'll put the thing back to settle it down. Once you go all the way back up there, Heatran will be in the place of the Magma Stone, and it is at level 70.
#486 - Regigigas
Regigigas can be found at the bottom of Snowpoint Temple. However, it will only appear if you have Regirock, Regice, and Registeel in your party. You will have to either trade for them or transfer from an older game to get them.
#487 - Giratina
After obtaining the National Dex, you might notice a new extension to Route 214. This takes you to Spring Path and a small fourth lake, Sendoff Spring. The cave in this lake is called Turnback Cave and is filled with fog. This cave is an unusual maze with a random quality to it, meaning that the same passage won't necessarily work twice. The goal is to go through multiple rooms and pass three pillars before you get up to thirty rooms entered. If you choose a door you entered from, you'll be back in the entrance room.

Solving which door to go through can be easy or difficult. Rooms have a symmetrical pattern to them, and the door to enter is the one that does not have a matching pattern around it. In some cases, it is near impossible to figure it out, so just choosing any door (other than your entrance one) will help. Thirty is a lot of rooms to go through, so stacking up wrong doors won't hurt much at all. The second number on a pillar will tell you the amount of doors you've been through.

As a hint for catching Giratina, bring a Normal/Flying type like Staraptor, as it is immune to all of Giratina's offensive attacks except Slash. Also, if you come back to Turnback Cave after you defeat/catch Giratina, you can find an item where Giratina was, depending on how many rooms you passed through. 3 rooms yields a Reaper Cloth, 4-15 yields a Rare Bone, and 16-30 yields a Stardust.
#488 - Cresselia
In Canalave City, go to the house of the Sailor that will take you to Iron Island (next to the boat). Inside, his son is trapped in a nightmare. Talk to the people and find out that you need the Lunar Wing, which can be obtained on Fullmoon Island. Talk to the Sailor and sail to the island. Go through the path, and you'll see Cresselia. It will fly off and leave the Lunar Wing you need. After that, you can find Cresselia in random routes, just like Mesprit. Once you return to Canalave, don't forget to heal the boy.

One way to make catching Cresselia (like Mesprit) easier, is to find where one Route ends and another begins. As you switch between routes, check the marking map until you are on the same route. Once again, however, putting the Pokemon to sleep will not prevent it from fleeing the battle, so act quickly.

Event Pokemon

Some Pokemon must be obtained via special Nintendo Wi-Fi Events. You can find a breakdown of those events on that page. Below are Pokemon from in-store and WFC events.

#386 - Deoxys
          Deoxys became available for download for Diamond & Pearl in America on the weekends of June 20th - 22nd and June 27th - June 29th, 2008. It was distributed at Gamestop and arrived at its normal form. Its level 50 in a Cherish Ball, the OT is Gamestp and the ID is 06218.

It came holding Nevermeltice, and with four moves it cannot learn in Diamond and Pearl until much later levels - Psycho Boost, Zap Cannon, Iron Defense, and Extremespeed. It is unknown whether this event will be available in other countries or not.

Deoxys can be changed into any of its other formes by visiting the four meteorites in Veilstone City.
#490 - Manaphy and #489 - Phione
    To obtain Manaphy, you need a second DS and a Pokemon Ranger game. Trade the Egg over wirelessly and go to a PokeMart to receive it. After that, simply hatch the Egg. This can be transferred without the National Dex, and for details on getting it in Ranger, check out the Ranger page for it.

After you get Manaphy, you can breed it with a Ditto to get a Phione. There's nothing special about getting it, and its stats are equal to Glalie's, the Pokemon that defined mediocrity in RSE.
#491 - Darkrai
Darkrai was obtainable at Toys R Us via Mystery Gift in the United States on 5/31/08 and 6/01/08. The OT is ALAMOS (female), and the ID is 05318 or 06018, depending on which date you attended. Its attacks are Roar of Time, Spacial Rend, Nightmare, and Hypnosis. It holds an Engima Berry and has a classic ribbon. It is very similar to the Japanese event.

After receiving the Mystery Gift, go to a PokeMart to receive your Pokemon.
#492 - Shaymin
Shaymin was obtainable at Toys R Us via Mystery Gift in the United States between 2/8/09 and 2/14/09. After receiving the Oak's Letter in a PokeMart after an event, go to Route 224, the extension route from Victory Road. At the end of the route, there is a white rock with Professor Oak nearby. Talk to him and Shaymin will soon appear and run away, letting you chase it down a really long, flowery path. Eventually, you'll catch up to it and be able to battle.
#493 - Arceus
By another event, you can receive an Azure Flute at a PokeMart. With this item, go back up to the Spear Pillar where you faced Dialga/Palkia. Select to play the flute when you’re asked to. Make sure that you save the game before you reach the top of the staircase that appears because everything afterwards is automatic. Currently, this event has not taken place.

Other Pokemon

#425 - Drifloon
Once every Friday, a Drifloon will appear just south of the Valley Windworks. If you don't catch it, don't worry, as it will come back every week.
#442 - Spiritomb
First you need to obtain an Odd Keystone, which can be found in a few ways. The easiest is by talking to a Black Belt in Route 208. Another is hidden in Twinleaf by the pond (use the Poketch App). And more can be rarely found by digging in the Underground. After you get one, go to the southeastern corner of Route 209 and insert it in the Hallowed Tower. Next, you have to talk to 32 players in the Underground (or one player 32 times, two players 16 times each, etc.). Go back to the Hallowed Tower and battle Spiritomb.
#479 - Rotom
Once the National Dex is obtained, go to the Old Chateau near Eterna City's side of Eterna Forest between the times of 8 PM and 4 AM. Inside, you may find a few spooky-looking things, but go into the room straight ahead. In this hallway, go in a door two to your left and check out the television. Rotom will appear, and there's only one.

-thanks to tiger10x for the info

 

 

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