You control Ghostly Wings even while it enchants an opponent’s creature. Only you can activate the last ability of Ghostly Wings.

After the last ability of Ghostly Wings resolves, it will be an Aura on the battlefield that isn’t attached to a creature and will immediately be put into its owner’s graveyard.

If Ghostly Wings leaves the battlefield before its activated ability resolves, the creature that was enchanted immediately before Ghostly Wings left is the one that will be returned to its owner’s hand, if it’s still on the battlefield.

You can activate the last ability multiple times to discard multiple cards. Only the first ability to resolve will have any effect.