You can obtain it without the raven cove quest being completed only cursed blades cannot be obtained, I got silver freeze from smasho and it only took 2 kills just use grenades don't throw the grenades directly at him just throw them at the side of him so he doesn't start attacking, if he attacks you and you kill him the loot will be on the bottom of the cave and I doubt there's enough time to get to it so again just throw grenades to the side of him ( basically don't look at his hp while you attack him )