Subtrain
Subtrains are a new technology powered by clockworks and magic that gets you safely from one island to another. Much safer than any explorer and mistwalker could ever provide you. So far, they are the most secure way to travel long distances, which also mostly means that they are mostly used by the rich and powerful. And the servants of course, servants know and hear anything and can get anywhere without great notice.
While there had been some experiments with train power and long distance travel before, it all mostly ended as mere experiments as most of the islands are not big enough for the giant investment of constructing a railway to pay off. The only train routes that are operational are connecting the ends of the main island, but are more of a tourist attraction than something you'd use for travel. Or a way to transport goods and post from one corner of the civilised world to another.
The secodn reason why most long distance travel goes nowhere, is The Mists. Because of their shifting and magical nature, they are too unstable to sustain any construction long term, as you never really know where you end up. Should you want to venture into the world, you have to hire a mistwalker or some seasoned explorer who will be able to get you were you want to go on a budget.
Subtrais, as the name suggests, tried a different approach. The magical effects of the mist seem to be null underground and while it took forever to adapt the trains to a subterrain mode of operation and to make the tunnels that would sustain them, it was proven possible about a decade ago. Ever since then the subtrains gain on popularity and we can expect that more of the world will become connected as other countries start to invest in this industry.