The wall was oriented vertically with respect to the caster and did not move once created.[note 1] The shape and the flaming side of the wall was determined by the caster and the maximum size of the wall was determined by the caster's level. The sheet of flame lasted for as long as the caster maintained concentration, or for a minimum time if the caster became distracted. The opaque curtain appeared 20 ft (6.1 m) high and reddish-blue to violet in color if created by arcane magic or greenish-yellow to amber if created by divine magic.
Any creature near the flaming side of the wall was subject to harm from the heat, although the farther away, the less intense the heat. Any creature passing through the wall suffered greatly—undead and other creatures susceptible to fire got the worst of it.
Verbal, somatic and material components were required to cast this spell, including a small bit of phosphorus for arcane casters. Divine casters could use their divine focus or holy symbol. Some druids use mistletoe as the material component of their spells.