|Although this article is based on canonical information, the actual name of this subject is conjectural.|
Incurso was an offensive disruption spell that was used to hex opponents. The spell required only an incantation, which roughly translates to "to attack" or "to invade" in Latin. The spell was cast through the caster's mouth and appears as a green gas that envelops its target. The spell caused magical damage or, at the very least, disruption.
In 2002, Giles, empowered by the Devon Coven, used this spell in his duel against Dark Willow. The effect of the spell was short-lived. Whether this was intrinsic to the spell or because it was used against an extremely powerful opponent, or both, is unknown.