Blade of doom

Blade of doom, also known as Shaeroon's scimitar, was an evocation spell that threatened one creature with injury from an invisible sword of force which was triggered by a condition chosen by the caster.

Effects
This spell was a curse that followed its target, hovering over the creature's head, waiting to strike if the trigger condition occurred. The sword of force was invisible except to the caster, individuals that could see invisible objects, and to any who cast a successful detect magic on the unfortunate creature. The trigger condition was usually some action that was undesirable to the caster, such as drawing a weapon or beginning to cast a spell. This spell could last up to one year.

The target did not get a chance to resist blade of doom until the curse was triggered and the blade struck the target. At that time, if the creature managed to resist the spell, no injury was received. Otherwise, the damage was proportional to the level of the caster. This curse could be removed before the expiration of the spell by the caster or powerful magic such as a limited wish. A normal dispel magic had no affect on this spell. Only one such curse could be put on a single creature at a time.

In practice, this spell was used as a punishment for those who drew the displeasure of a powerful wizard. It could also be used during negotiations to encourage honesty or discourage treachery.

Components
In addition to verbal and somatic components, this spell required a small model of a scimitar made from rock crystal (with a value of 300 gp), diamond or colorless sapphire (valued at 3,000 gp).

History
This spell first appeared as Shaeroon's scimitar in "The Book of Bats", part of the treasure looted from a satrap in Calimshan over 200 years before the Time of Troubles. It was also found in "Tidings of Conflict and Woe" under the name blade of doom. This spell was eventually published in "Volo's Guide to All Things Magical" and became generally known to the magical community.