The largest obstacle to shipping in the past few hundred years has been the Felann Empire. They have reigned as the undisputed champions of the seas for all that time mostly because of their very early development of smoke powder and quick ships. These clippers, armed with cannons and shielded in metal armor, were the match for anything that the peoples of Asterland could build, on the order of ten to one. The merchants who rely on shipping to extend their reach for trade purposes usually had to rely on the use of powerful wizards to make up the difference. This cost them so much that only the most valuable cargo could merit spending that kind of money.
In more recent years, merchants have taken to the skies for transporting goods. While also spendy, requiring the use of a mage to man the magical draining helm for its propulsion, it removed the danger factor present with traditional shipping. That is, it did until the desert rats and others began to take to the skies as well, especially in the slipstream, a powerful jet stream of wind that circumnavigates the globe. It is the only way to traverse the long distances effectively in lighter-than-air craft, by far the cheapest way to transport goods from continent to continent. By use of the slipstream, one can circumnavigate JERA in a matter of a month in a lighter-than-air craft manned by a skilled crew, but not requiring a mage for propulsion.
So it is that merchants seek cheap transport of goods still. A new magitech means of travel has caught the eye of the merchants. Dwarven engineers in Greymalkin created a submersible ship. While under the water it is far slower than the Felann craft, its ability to defend itself makes it more than a match for the quicker ships. Gunthar Enginemaster created the craft to aid in the unspoken war between the felann and the merchants. The first of the craft, the Leviathan, was well built, but unreliable. On its maiden voyage, however, it proved its worth by destroying a dozen felann craft with its powerful top-mounted auger. Diving beneath the enemy ships, it would drill large holes in the mostly unprotected bottoms of the ships, sending them to the bottom of the sea. The Leviathan was destroyed when mechanical problems forced her to surface, where she was blown apart by the enraged felann.
While no war was ever declared agains the felann, which operate their pirating ventures with neither the assistance nor blame of the Felann Empire itself, the felann ships began to arm themselves more and more with crude depth charges (barrels of smokepowder with a waterproof fuse). The Dwarves build the submersibles much sturdier than before, able to take all but a direct hit by the explosives. Once they are attatched to the bottom of a ship, however, the charges will also destroy the felann ship that they are attatched to.
While the felann are still the terror of the seas, their exclusive ability to sail the seas unmolested has begun to fade somewhat. The Magic Works, a magimotive giant, now builds the submersibles and charges to escourt cargo ships safely through felann waters. For the time being, shipping is moving more and more undisturbed by the pirates, but the felann are crafty and are already working on more advanced countermeasures with the help of former punker anarchist wizards. Certainly, this war will go on for some time, the balance of power shifting one way, then the other.
The Felann Empire is reluctant to get involved for fear of starting a full-scale war with Asterland, of which Greymalkin is the southernmost city, a military outpost turned city. They fear the wizards of Asterland more now that they have the ability to store magic and to channel more and more of it by a single wizard with the use of focal amulets. Also, they are comfortable with the taxes that they have exacted on the pirates over the last hundreds of years, and this leisure has led to laziness in the government. The Empire has more than its share of internal struggles. Each island is its own state, declaring sovereignty to the Empire, but fighting with one another over tiny islands and who controls what waters. If this remains the case, the Felann Empire will not be a threat for long to come. Their navy is strong, but they see no reason to risk it to fight the battles of the pirates.