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. 

When casting a spell an area of effect spell with a duration of instantaneous with this foci you may choose to reduce the area by half (rounding down to the nearest 5), if you do this the save DC increases by one and any damage dealt is increased by two of the spells damage dice.