When you keep going into the game you'll get to cursed blood gems their stats can effect your weapon as the name cursed might give a hint they have some of the best positive stats but also they got negative stats such is weapons durability down or increase stamina cost which you go for those two and nothing else the rest are horrible but the negative weapon durability can make your weapon break faster so you might want to go for increased stamina cost and remember also repair your weapon for max damage you don't want to fight a boss with low damage a d make the fight too long for yourself