Notes from author
Be wary of incoming wall of text.
Build for invasions in Anor Londo or higher - I use it mostly for the painted world since when I am done with the build, I am there anyways (well cept for the parry dagger. You would be surprised how much damage it does, especially when you use it to inflict extra riposte damage or go for infinite stunlock R1L1R1L1)
You can swap out hornet for Leo, but note that magic damage is not increased by a counterhit (Riposte/BS however does), therefor the leo only gives you a lousy 40 extra damage on counters (ok its a rapier - but still).
Also two-handing this thing seems to inflict about 50% more damage despite it having an E scaling in Strength.
Karmic Justice is more viable than you might think - it is absolutely great to kill wheel skeletons for example, or any other spamming attacks (such as ricard's rapier or homing soul mass).
However with this build it only does about 300 damage since the magic damage of the rapier is not that high.
Vow of Silence is good against Coopers or Gankers, and you dont have any spells to use anyways.
Should you go high level with this I recommend 41 end, swapping out to black iron leggings, increasing int and vit, getting one more attunement slot so you can use wog.
Velka's talisman is more effective than any talisman if you got higher int than 31 and fth is at least 5 points lower.
For the spells with this setup you dont need mag adjust anyways (KJ scales with right hand magic damage, Vow of Silence is time based).
This build is also deadly against people with no poise who rely heavily on magic (prime example: Jeremiah).