Derived from the weapon charms of the crossroads. As an action, you may attach a foci charm to a foci of your choice such as a druidic focus, holy symbol, bardic instrument, component pouch or arcane focus. You may detach a foci charm and reattach it to a new foci as part of the same action. A foci may benefit from only one weapon charm at a time. 

While concentrating on spell cast from this foci you gain a +1 bonus to your armor class and saving throws.