The Mark#1:the prophecy

I live in a world where the great dragons head is on my sword but lets go back twenty years and 11 months I was fighting with the greatest dragon he almost killed me for betraying him saving a dog. He was furious and killed almost everyone in the town the next day. I came across a bunch of heroes luck,earth,animal,life and death marked we killed him but who arose was the great dragon he was way bigger. I heard him casting a spell if anyone but me killed him they would have killed every human except me. The longer time I took the stronger he got I used the mark of the dragon against the greatest dragon why not against the great dragon. This needed a dragon blade to preform and mine was crushed but I think I lost a tooth in the war. The dragon blade cuts through even the strongest material. Sorry I am ellis a young adult who always slays beasts.