Armor of Agathys

Armor of Agathys is a complex spell learned and used by young or inexperienced warlocks. When armor of Agathys is cast, it creates a layer of thick, black ice around the body of its caster, adding to their vitality for several minutes and injuring enemies who draw to near with its frigid power, the deadliness of the ice depending upon the durability of the warlock. Armor of Agathys draws heavily on a warlock's power and it can only be cast once per day.