Finally got it!
After trying 1 week, I was watching bleach, then I tried to farm the pure bladestone again, and I got it!!
I screamed so loud I thought my lungs were gonna explode!
I hate trophies based on luck..
Now I need the pure darkmoonstone!!
Wish me luck!!
Sorry to bump this back up from the grave but its that time again and its the last upgrade stone I need to get my 1st platinum. Anybody willing to part me their spares, as I've been tirelessy farming for these "unicorns" this whole past week offline to avoid the "Online WT equlibrium system". I have two characters at Soul Level 7 and 20 but I can always dupe glitch the beasts soul to increase my level to match anyones.