Shadow Leech

Shadow Leeches were creatures that were created by the Brotherhood of Makuta to drain Matoran Universe beings of their inner Light.

Description
Shadow Leeches were small blue creatures with spherical bodies, two eyes, prominent fins, and a large row of visible teeth. They were created from the mutation of Kraata, so like Kraata, they were comprised solely of organic antidermis. Shadow Leeches existed only to drain the inner Light of Matoran Universe inhabitants, which they did by instinctively targeting beings with inner Light, attaching themselves to them with their teeth, and absorbing their Light through physical contact. Before detaching from their victims, Shadow Leeches also created a psychological barrier that stopped the victim from naturally recovering their inner Light. Shadow Leeches would typically detach themselves when they had drained all Light from their victims and would be disintegrated by the Light energy that they absorbed over the following ten minutes.

Shadow Leeches did not have independent locomotion because their fins were too small and useless to move with, so they were typically delivered by Makuta, who would throw or drop them on their targets.

The Matoran Universe inhabitants who had their light drained by Shadow Leeches manifested Shadow powers and developed selfish, malicious, and megalomaniacal personality traits, which the Brotherhood of Makuta believed would cause them to abandon any preexisting morals and join the Brotherhood, where their goals of conquest and subjugation could be achieved.

Original Universe
The Brotherhood of Makuta created Shadow Leeches through the mutation of Kraata to further their goal of conquering the Matoran Universe.

Before or during the Vrai War, Caiaphus created his own personal army of Shadow Toa by draining their inner Light with Shadow Leeches. This was one of the reasons he was exiled from the Matoran Universe.

Shattered Mirror Universe
SM Ynot used Shadow Leeches to turn the Light Hunters into the Dark Hunters during his campaign to take over the Matoran Universe.

Trivia

 * The Matoran classified Shadow Leeches as Rahi because they were non-sentient creatures that lived inside the Matoran Universe. However, they were not true Rahi, because they were made of organic antidermis instead of protodermis.