So what is it?
Manifestations (or MFS because the author believes having an acronym makes you cool) is a fantasy series originally written for the LJ community runaway_tales. It is told in serial format over a series of arcs.
The story is that of Jen and Dhaymin Dhalsiv, two brothers whose lives are changed by a monster hunt gone very wrong, their search for a cure for Jen's blood-curse, and the people they meet along the way.
Manifestations is set on Sena, a world distinct from our own. More specifically it takes place across two neighbouring nations, Rhusav (where the protagonists originated from), and Toxilivital (where they hope to find Jen's cure). In theory there's supposed to be a lot of worldbuilding background, but it mainly consists of the author obsessively making maps.
Sena is low tech at the time of Manifestations and can be said to fit the "medieval fantasy" mold, though it's the handwavy, general low tech, not any specific culture sort. You will also not find any dragons, elves, dwarves, trolls, orcs, wizards, or any of that hanging around.
So what will you find? Wild taiga forests, cities shaped like pyramids, monster beasts that bond to people with blood, mind-shattering frozen voids, and snow. An awful lot of snow. A key concept is the idea of "tarnishing" - that monsters, when bonded to people, can slowly take over their mind. And then there's the "beast hunters" - people who for whatever reason (fame, glory, to avenge a loved one's plot convenient death) make it their living to seek out and kill such creatures and those bonded to them.
This is the life that Jen and Dhaymin were born into, and the plot kicks off when Jen finds himself tarnished. Now they're on a quest to find a cure... or a good library. Whatever works.
There's also the fact that said blood-tarnishing monsters weren't always around...