I would highly prefer Quick Ball or Ultra Ball. But, first thing's first.
Go get a Pokemon that has a move "Block" ,"Mean look" or any Pokemon that can stop cresselia from escaping. These are the Pokemon that has the move that can block:
Bronzong - Location: Mt. Coronet (Near the Peek!)
Zubat - Location: Any Caves like the One near Jubilife City
Wobuffet - Location: Lake Valor (Use surf and go to the Bottom-Right of the lake)
Also, you can look for mesprit at your Pokewatch, On the Pokemon Pad, You should see a Kitty Head on whereverplace. DO NOT FLY TO THE MESPRIT!!!!!!!!!!!!!! it will fly to a different location!!!!!!!!!!! After he runs away, Rowan asks you to get a Marking Map so go get that in Jublife City in the Pokétch Station.
After that, turn marking map on and don't fly to the cities. You have to walk that gives a 90% chance that it doesn't escape far if it does, fly to the city where there is a little red spot blinking around, fly there, and go a little out of city then Mespirit maybe comes a little closer. When it shows up you need a Pokémon with Mean Look, Block or Wobbuffet's Shadow Tag Ability so that it can't escape or you can use a Master Ball on it. all i did was used crunch, then it ran away, used crunch again until HP was red, then it ran away, then i used grass whistle so it would fall asleep, then it ran away, then when I met Mesprit again, i threw a quick ball and it caught it. I do this every time and it works every time. Sometimes you are just unlucky. Make sure to save a ton when you are mesprit hunting if you really care about catching it. you might get a critical hit or something. DO NOT USE MASTER BALL IF YOU HAVE ANY HOPES ABOUT CATCHING CRESSELIA, FOR IT IS WAAAAAAY HARDER TO CATCH!!!!
just go to the Pokemon league
after you relese uxie,azelf and mesprite
yes if you dont catch them
zapdos get it in the end of the game when you complete pokedex catch like mesprite
Mesprite is at Lake Verity in the small cavern in the centre of the lake. Hit A to battle and then it will flee.
It is never seen again,or that's what I think.
Uxei doe not run, mesprite does. mespriet is one of the running Pokemon much like entei, raikou, and suicune in gold and silver. if you look on your marking map you will see a Pokemon symbol, that is where mesprite is, however mesprite will move if you change locations.
heatran dialga palkia uxi mesprite
surf until you get to the cave in the middle of the lake and mesprit should be there
Uxie , Azelf and Mesprite can be caught on land or a lake
uxie groudon mesprite azelf and dialga
the best way to catch creselia is to weak it and when its hp is red catch it with a quick ball.the quick ball must be used when you find the Pokemon and throw as your first ball without a move the best way to catch mesprit is to throw your master ball at it. (i havent caught creselia yet.) or you can use a masterball on both if its hard ue a quickball on either when their weak(i havent caught any of them im trying though)