Beltyn's Burning Blood (Necromancy)
Level: Bard 4, Mage 4, Sorcerer 4
Range: visual range of caster
Duration: 5 rounds
Casting Time: 5
Area of Effect: 1 creature
Saving Throw: neg.

By means of this spell, a wizard can cause the open, bleeding wounds of any creature to burst into flame, converting the blood into a corrosive mix that inflicts 3d5 additional points of damage per round. "Open wounds" is defined as those wounds created by an edged weapon that have not been dressed or healed.

Obviously, the creature must have blood in the first place in order to be affected by this spell. This excludes undead and extraplanar creatures that do not have obvious blood (like elementals). Similarly, creatures that are resistant to fire are immune to the effects of this spell.
Each of the three rounds the spell is in effect, the target can make a saving throw vs. spell with a -3 penalty. If the save is made, no additional damage is inflicted by the spell.

The caster does not need to touch or even see the target, as long as the individual meets the requirements above and is in the range of the spell. Individuals in the Ethereal Plane are immune to attacks from the Prime Material, but not from attackers on their own plane. Creatures that have changed shape or passed into other objects (such as a tree or rock) are still vulnerable to the spell. Creatures and individuals with regenerative abilities or spells can save at the normal changes to prevent further damage.

Spell Focus: a pinch of saltpeter.