Notes from author
First of all, I'd like to say that the Crystal Greatsword is crap at any level past 70. It can't be upgraded, it can't be buffed, and it's stuck at 190 base damage, and with CC scaling, that gives it only 325~ damage. Meanwhile, a bastard sword as a similar moveset, is stronger, and can be buffed. It's not 100% accurate, and I would give up viability for accuracy, but the Crystal Greatsword is comparable to the Drake Sword. I'm sorry. There is also no Crystal Bolts, so Crystal Avelyn is a no-go.
But other than that, this build has a nice theme going for it. The Crystal Bastard Sword when buffed has an AR of about 1k. Great INT means powerful Soul Masses, and high Dex means you can pull them up in the middle of battle. The Avelyn is very good, it breaks poise like Torch Hollow. Sadly, you're not in the best armor, nor in the best range of vitality or stamina. Play carefully.