Flamsterd's flamestrike

Flamsterd's flamestrike was a specialized fire spell that was used either as an offensive spell or a trap.

Effects
The spell would create a spiral of fire around the target, and was able to target a single creature only. The spell interrupted any spellcasting by the target and would cause damage even if the target was magically protected from fire.

When used as a trap, the spell must be cast on a piece of metal, such as a coin. The caster would then set a series of triggering conditions, similar to magic mouth. These conditions could not involve actions such as entering an area or casting a spell. This trap was immune to magical detection spells, and could only be detected magically if the target was considering an action that was also a triggering condition.

The trap lasted indefinitely until one of the triggering conditions were met. If dispel magic was cast on the trap, the spell would expire. The trap only targeted a single creature, chosen at random.

Components
In addition to verbal and somatic components, this spell required several material components. The caster needed a pinch of both saltpeter and ashes, a small piece or filings of any metal and a piece of phosphorous.