This spell created tiny beings from the caster's blood. They were linked to the caster, allowing the caster to experience the world through their senses as well as his own.
Upon casting the spell the caster gave themselves a small cut. The droplets of blood from the cut assumed the form of small animals under the command of the caster. The animals were small enough to fit under most doors but the moved extremely fast. They could also seep through any crack or tight opening that water could penetrate.
This spell was useful for spying on others, or examining a locked room. Any spells cast upon the blood affected the caster as well.
The blood animals could attack targets, causing blindness if they successfully struck the eyes. The blood burned like acid wherever it landed on a target.
Regardless of the circumstances, using the blood to attack a target was considered an act of great evil.