Your witch knife is as much an extension of your body as it is an extension of your power.
Prerequisite(s): Witch Knife.
Benefit: You can use your witch knife as an additional focus component for all your witch spells, not just your patron spells, adding 1 to their DC. This bonus stacks with the bonus to patron spells granted by Witch Knife, granting your patron spells a total +2 bonus to their DC.
Additionally, the hand holding the witch knife is still considered free for the purpose of casting spells and delivering touch attacks.