By using Barricade before channelling health into the prism, a player can charge up a crystal for themselves or others at no health cost. Penance aura will grant prayer points for health lost to the prism. When the player reaches 1 health, all health would be automatically refunded, resulting in a net gain of prayer points, making the prism a nearly unlimited, but risky supply of prayer. This spell can't be used in Fist of Guthix.