"Well, obviously, travelling to the underworlds, the myriad lands of the dead, is very easy. Grab a knife, pick a vital organ, insert, and you're there. Travelling there in such as way that you can travel back again, that's a bit harder.
I do know of a spell that will let you do that, open a portal to the beyond. While the spell itself is not that hard, barely more difficult than a good old fireball incantation, it does have some... challenges associated with it. For starters, the spell won't work anywhere on this world. Thankfully, you can get around that by sailing to the very edge of the Coin, casting the spell so that the portal appears off the edge. Best to make sure you're going at a fair clip when you do it though. You don't want to come up short and fall into open space.
Oh, and if you think sailing a ship off the very edge of the world is difficult, just wait till you try coming back..."