There are charms that power up certain weapons and certain spells (e.g. the accessory you found makes the Prism spell's red shot set enemies on fire). Vampire's Mirror powers up Throwing Glass, several of the bee-themed charms also powers up bee weapons and each other (e.g. more shots from Bee Spear and Bee's Knees), the "increases strength" bell charm makes all thrown weapons deal extra damage and lets you move faster when carrying something, etc.