Athames or ritual knives are a witch’s personal, magickal tool used for casting the circle, invocations, evocations, calling the watchtowers, spell-work, ceremonies, and various rituals and rites. Tradition states to use the tool as much as possible to increase its power. The athame is associated with the element of fire. 
Selenite is a cleansing stone. While cleaning negative energies, it can reprogram other stones. It helps for mental clarity, and for connecting with the divine. This stone is also used for exploring the past, present, and future.