Go after another strong pokemon, for example. That far into the game there is not much you have to do.
If you got the Member Card from an event (or cheat or however), you could catch Darkrai by visiting the house right at the waterfront of Canalave City.
Chat with our AI personalities
Yes, you can, but it is confusing, not knowing which is which. It is easier catching Mespirit then attempting to catch Cresselia
confuse it or put it to sleep.sleep her or master ball
It will keep fleeing unless you have a Pokemon with Mean Look or something like that so it won't escape. Try catching a wild Golbat. The same is for Mespirit.
If Cresselia disappeared off of your map completely, then you have already caught Cresselia, or there is a glitch in your game where Cresselia has just disappeared off of your map. Further details would be needed for a more in-depth assessment as to why this has happened if neither of the two reasons stated are why Cresselia isn't on your map.
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