Sirius a knight who is completely the opposite of it's name

In a world where all kingdoms fight for land each kingdom fight and tries to convince a single man because of it's unmatchable intelligence and strength yet until now no one succeed as this man lives in a mountain which is full of corpse and bones of those who he have killed

You are the new successor of the kingdom of Catariah and it's now on your hand on how to protect your kingdom or if you will convince the knight of death