This spell creates a magical sphere around the caster which prevents any first, second or third level spells from penetrating, i.e. the area of effect of any such spells does not include the area of the minor globe of invulnerability. However, any sort of spells can be cast out of the magical sphere, and they pass from the caster of the globe, through its area of effect, and to their target without effect upon the minor globe of invulnerability. Fourth and higher level spells are not affected by the globe. It can be brought down by a dispel magic spell. The material component of the spell is a glass or crystal bead.