The Starline Cruise sends out invitations, through mail or birds or flashes of fire or whatever seems appropriate. The invitations are always magical and often impossible with the world's native magic. The invitations come with whatever you need to get to the cruise's location, train tickets, cash, occasionally a magic teleporting rock.
Your cruise is of varying length, but no matter how long your cruise is, you will always return the day after you arrive.
The ship arrives on water if it can and through the sky, if it can't. It it golden-bronze and feathered and covered in the lights from a thousand windows.