Black Beast Lord, start by capturing the Dark Elf Knight alive

Ostia is the only and largest continent on the planet, where danger and opportunity coexist. However, the originally peaceful life has become strange because of the appearance of monsters in the north.
Those monsters are a huge threat to any race. Humans, dwarves, and elves are all targets of killing and humiliation by these monsters.
They would abuse their bodies and plunder their property as the ultimate enjoyment. Some of these monsters would even treat other races as food.
So, the war began, and the Human Kingdom, Dwarf Kingdom, and Elf Kingdom bordering the north signed a non-aggression pact and built seven fortresses on the border to resist the invasion of these monsters. These seven fortresses were called the Seven Shield Fortresses by the world because of the alliance!
They are the strongest shields against those monsters!
The long war lasted for a thousand years, and no matter how hard they killed, the number of monsters never decreased. Out of desperation, the human kingdom opened a law from a thousand years ago, allowing pioneering knights to appear!
This story begins in Shivaash, a territory of pioneering knights.