The cauldron is weird. Though it kind of suits Nagacity better...
I'll still go with Mage Fist.
Cauldron seems a bit... situational to me. Potions kind of weakin it with the removal of manaburn/poison, though if you just use one potiontype and no dings... hm. like the Magefist more. Dunno, if retaliate is physical I could imagine something like a caster monk with it, which sounds awesome.
Bah, keep both. Put the Cauldron into Nagacity and the magefist somewhere else.
I like it how Magefist is put under ""