This is a WIP map of a continent in my world:
The small portion of land you can see in the topmost area is another continent, to the north of which the sea is almost always frozen and thus almost impossible to navigate.
The strait between the two continents is temperate, but on the other hand it's controlled by a single entity, which can impose trade tariffs as they please.
Since the entire eastern coast of this continent features an almost-impassable mountain range, traders coming from the east will probably be inclined to sail south and circumnavigate the continent, avoiding both the mountains and the tariffs.
The traders I'm interested in will be coming from another continent located to the east (not pictured). Their goal is reaching the continental area to the west of the mountain range (so, basically 95% of the continent) and a few more islands to the west. Picture this as some kind of Silk Road, where "fantasy China" is in the middle of this continent.
What could this southern sea be like, in order to discourage traders from trying to circumnavigate the continent, and instead force them to choose between paying the tariffs and trying to find a way through the mountains?
To be as clear as possible, my end goal is that the strait tariffs and the mountains will be the only viable solutions, not just preferable, and in the end due to political rivalry ("there's no way we will keep paying those tariffs!") the empire from which most of the merchants are coming from will decide to build a tunnel through the mountains, as in the other question of mine (linked), rather than having the possibility of just taking the southern route.
The more "original" (as in "woah I hadn't thought of that!", not necessarily something totally unique and never heard of) the idea - while preferably being simple to explain - , the better. So the best answers would either be ones with a lot of ideas, or a really cool and interesting one. In the end I guess the accepted answer will be the one containing the suggestion I end up using :)
Note that this is a medium-high fantasy medieval setting, so magic stuff isn't prohibited, as long as it makes sense (made-up megafauna = okay, "oh there's just a generic magic tornado always spinning around there" = meh)
The technology is comparable to 13th-century Europe.
What I have thought of so far:
- dangerous megafauna (intriguing, but could pose more worldbuilding problems: why is it only in that area?)
- ice (I would rather not; this area should have a temperate climate)
- pirates (sounds a little dull maybe?)
Note: Answers to this question surely help, but it's far more grounded and focused on realism, having the science-based tag. In my case, fantasy explanations (as long as they're not far-fetched and are sensible - as in "can be explained so that they sound plausible in a fantasy world") are more than welcome.