Shadow leeches were a form of mutated kraata created by Mutran which could drain the light of any living being.
By experimenting on kraata, Makuta Chirox was able to create shadow leeches. These creatures could actually drain the light out of anyone they made contact with. Once all light was drained, the victim turned evil and allied with the Makuta. Shadow leeches had a limited lifespan, and like Makuta, they were vulnerable to light.
Mutran was the Brotherhood of Makuta's expert at creating shadow leeches and other strange creatures.
A shadow leech was a creature that could drain the light out of others and turn them to beings of shadow.
Mutran worked with his rival, Chirox, to create the shadow leeches and Tridax pods.