You can get the blood sword from gaffgarion at golgollada gallows by stealing it
but!!!theres another way to get it..
have byblos on your party (byblos has poach .dont know if the thiefs skill poach are the same)
you must poach a dark behemoth ..in the poachers den, youll find it
it only has 8 attack power but the damage you inflicted will heal you
so make sure you have the skill doublehand to deal 200+ damage