My theory on The River King

So here is what I think about The River King champion tease. First I will state a few facts:

The River King, from his name and appearance in the video is obviously some sort of amphibious creature.

He is carnivorous and has incredibly large jaws.

His conduct seems that he has an appetite for destruction.

He has some connection to the town of Bilgewater as it is shown at the end of the clip.

Now my theory:

The River King is the cause of the disappearance of Fizz's people.

In Fizz's lore it states that he ventured outside his home to seek adventure, he encountered many different creatures and gained great prowess as a fighter. It is possible that in his foolishness Fizz did not come by those skills naturally, he might have come across the River King who offered to train him to become a great fighter and Fizz, in his foolishness, accepted. Fizz might have been taken to some other land by the River King to learn how to fight. After some time the River King returned to Fizz's city to take what he thought was his. Seeing that Fizz was absent, most likely on an adventure, the River King turned the city's population. Upon revealing himself, the entire city fled in fear only to be chased down and eaten by the River King. When Fizz returned he saw no sign of his people, so he went to Bilgewater. He made a name for himself there and that is where the teaser comes in. The River King heard of Fizz's exploits in Bilgewater and being unsatisfied with the conclusion of his deal with Fizz journeyed to Bilgewater in order to find him; however, he found the young gambler first.

What do you all think?