WOW I have never heard of this legendary Pokemon it is called Cressila where is it help me plz
To get Cresselia, you need to go to Full Moon island after you beat the Elite 4 and after you talk to a Sailor in Canalave Town/City. After that, you enter the cavern and you see Cresselia, which will start to wander all over the Sinnoh region.
In pokemon d or p go to a sailors house in the town of the 6th gym leader. The house is near the pkmn center but lower. Talk to the sailor and he will ask you for help and leave go to him at the docks and he will take you to an island while giving you a lunar feather. Arrive at the island and walk to the top enter and fins crescelia.