How do you get the 3 legendary pokemon in pokemon diamond?

Answer 1

there are actually 7 legendary Pokemon obtainable on Diamond. They are:

Dialga, Giratina, Heatran, Mesprit, Uxie, Azelf and Cressilia. Regigias is also obtainable with out cheating but you need Regirock, Registeel and Regiice which you can't catch in sinnoh.

Rotom and Spiritomb are kind of legendaries.

Dialga is found at the top of Mt Coronet. Heatran is found in Mt stark, Giratina is found at the end of a cave which you can get to by going to the spring path, Mesprit Uxie and Azelf are found in the centre of the 3 lakes : verity, valor and acuity, and Cressilia is found on full moon island.

you can't get Giratina, heatran or Cressilia until you get the national dex/

To get to full moon island, after getting the national dex, fly to Canalave city. talk to the guy near the boat. he will say some stuff and ask you if you can get him the lunar wing (you might need to go into his house, which is near his boat and talk to the lady and the boy inside for him to ask you to get him the lunar wing). if you say yes he will take you to the island. you find cressilia there. press 'a' when you are in front of it. it will fly off and leave the lunar wing behind. then it will fly around sinnoh. to track it use the marking map application. Mesprit also flys around.

Rotom is found after getting the national dex at the Old chateu in Eterna forest, at night in a tv

Spiritomb is harder to get. You need to talk to 30 different people after putting an odd keystone in the crumbling tower on route 209.

The levels of the Pokemon are as follows:

Dialga - 45/47

Giratina - 70

Heatran - 70

Mesprit - 50

Uxie - 50

Azelf - 50

Cressilia - 40/50/70

Rotom - 30

Spiritomb - 30

Regigias - 70