Mesprit moves around the world at random so it could potentially be anywhere after it runs away. To find where he is, use the map on the Poketch.
You can't I don't think.
In map 22 (Ground)
The one you need to find mesprit is called the marking map you can get one from a guy in the pokech building in jubilife city (he has brown hair ).
You always start form twinleaf town right? So go to the lake closest to twinleaf, and use surf to go to a cave in the middle of nowhere, go inside, and you'll hopefully find a mesprit. Mesprit runs away from you, so I suggest you have a Pokemon with Mean Look.
Mesprit & Cresselia (legendary)
your home lake
You have to have beat the Cyrus and the Distortion World. Then go to Twinleaf Town and go to the lake by it. Surf to the middle and go to the cave. There you'll find Mesprit.
Mesprit moves around the world at random so it could potentially be anywhere after it runs away. To find where he is, use the map on the Poketch.
After you've defeated Dialga, you go to Lake Valor or any other lake, you surf to a cavern in the middle and in there you will find Mesprit.
Catch them?
You can't I don't think.
In map 22 (Ground)
You can find Mesprit in Verity Cavern. Head to Lake Verity and use surf till you find a cave. Inside will be Mesprit. However, it will run away so you will need the Marking Map app to find it.
you find them in the three lakes in diamond, pearl, and platinum.
You find them all at separate lakes. You can catch Uxie and Azelf at their lakes. Mesprit flees again when you go to her lake. You need to use the map marker poketch app to find it. PS: Don't fly towards the Mesprit. It will go to a different spot then. Use your bike or run to get to it.
The one you need to find mesprit is called the marking map you can get one from a guy in the pokech building in jubilife city (he has brown hair ).