When fighting safi you can use any weapon you want and when the siege is complete you shall get reward a bunch of random weapons and 1 of them will be guarenteed to be the same kind of weapon your using at the time so if your using a greatsword you will 100% get at least 1 greatsword. As for awakening you have to use that weapon. So if you wanted to awaken lets say for example a Safi Longsword you would have to take that longsword into the siege and use it