Ylang-ylang is an evergreen tree with very fragrant flowers.  Those flowers are used to make the essential oil.  It does not have a history of being used in religious ceremonies, but it's pleasant fragrance is known to be relaxing and balancing bringing about feelings of calmness and euphoria, which are good when pursuing spiritual development.  It also helps balance hormones and prevents mood swings. 
    Medicinally, it is know to help regulate breathing, heart rate and blood pressure.  It reduces fever and helps with symptoms of Malaria. On the skin, it can help with over-dry or over-oily skin.   It helps with anxiety, fear and panic attacks.  It also combats motion sickness and is a primary ingredient in the natural motion sickness product  MotionEaze.