Notes from author
Steely's favorite build. Not the best STR/INT build around, but it's damn fun.
The Man-Serpent Greatsword is a destructive powerhouse, plain and simple. It deals massive damage, and is incredibly effective at crushing guards, especially when two-handed. It absolutely must be respected.
Crystal Magic Weapon simply augments the MSGS's lethality, as it will increase it's power and allow it to inflict chip damage. No shield will survive long against this combination.
Armor isn't necessarily optimized. I just like the Dark set, and the MSGS doesn't look good with most of my other favorite armors. It's purely aesthetic.
As for rings, FAP is a requirement. Cloranthy is one of my favorite rings, as it supports offense and defense equally well. Feel free to replace it with something else, though, such as the Wolf Ring or Lingering Dragoncrest.
The three extra spell slots should be used to augment this build's versatility. Personally, I think Chameleon can be a dangerous tool, as it's not commonly seen in PvP. The MSGS's strong single strikes makes it ideal for ambushes, as well. Use the other three slots as you see fit.