Notes from author
Theoretical PvP mage build I drafted up that has a combination of big magic damage, a few trick spells, and repair magic for switching between Moonlight Greatsword and Channeler's Trident without losing durability. Nothing has been tested in terms of how well this works in game, but still it has a good arsenal available to it.
Velka's Rapier for quick jabs and parries.
Chameleon combined with Homing Soul Mass will aid in surprise attacks of unsuspecting enemies. Spell slots subject to change with testing.
Quick switch Bellowing Dragon and Hornet Ring if you successfully parry with Velka's Rapier.
Notes:
If poise is not an issue, switch out Havel's Ring for something more optimal and drop some of the unnecessarily heavy armor such as Black Iron. The weapons are still heavy, so Havel's is still recommended. Catalyst is subject to change after analyzing best choices.