I think you go and catch it in it's cave.
anywhere
No, you need to trade for it from Pokemon Pearl, Diamond, and Platinum.
The Legendary Pokemon in Diamond are Dialga, Azelf, Mesprit, and Uxie. That's all I know of.
You mean Mesprit? Lake Verity ( you have to free it from Cyrus and then chase it around) hope this helped! -Majbrit
If you have the marking map it will track mesprit, just don't fly.
walk out of the door!
There are only 3, Uxie, Mesprit, and Azelf.
No, you can't. To get it, you must trade from diamond, pearl, or platinum.
no maybe if you hacked
dialga,palkia,mesprit,azelf,uxie,giratina,heatran,
The Pokemon that can be caught without special events, trading, or cheating in Pokemon diamond are: Uxie Mesprit Azelf Dialga Giratina Heatran
You can get Dialga Mesprit Uxie Azelf Giratina and if you somehow get regirock, regiice, and registeel on to diamond you can also get regigigas