From Halopedia, the Halo wiki
Thanolekgolo is a subsistence gestalt of Lekgolo, and one of the six specific gestalt types known to the Covenant. The resident specimens on Halo Installation 04 were part of a failed plan undertaken by the Forerunners to defeat the Flood.
Anatomy and physiology
The Thanolekgolo specimens present on Alpha Shard exhibited several peculiar qualities in comparison to common Lekgolo. They had a particular sensitivity to active technology due to their ability to detect various forms of disturbances in the air, including magnetic fields, radio waves and electromagnetic pulses, from considerable distances. They could also sense movement, particularly at close range. They were very nimble and fast both by themselves as well as in some of their gestalt forms. The eels were able to jump small distances and exhibited considerable teamwork even in the process of coalescing in and out of their various colony assemblages. They were highly vicious in their behavior and mercilessly devoured any biological organisms and technology they encountered.
Plans against the Flood
During the Forerunner-Flood war, Thanolekgolo were attempted to be used against the Flood, where ultimately they were stored as specimens on Installation 04. The Office of Naval Intelligence later speculated that the Thanolekgolo's unique sensitivities to electromagnetic radiation may have been intended by the Forerunners to use the Thanolekgolo to destroy technology captured by the Flood before Forerunner military forces were sent to eradicate the infestation.
Discovery by the Covenant
Events on the Alpha Shard
Following the events of the Battle of Installation 04 that ended in the ring getting destroyed in September, 2552, a portion of the ring called Alpha Shard was sent to a planet some distance away from the Orrichon system. Where a recon drone called Recon-14 from the UNSC Pillar of Autumn survived the battle and recorded footage showing evidence that life was still on the ring, right before it was destroyed by said life.
This life on the ring turned out to be Thanolekgolo, and their sensitivity to active technology caused issues for people going to Alpha Shard, eventually trapping Locke's team and Sedran Colonial Guard forces on it when they attacked the D81-LRT Condor. This led to the Thanolekgolo proceeding to hunt the humans on the ring, until their escape a few hours later. The Thanolekgolo were destroyed when Colonel Randall Aiken sacrificed himself to detonate a HAVOK tactical nuclear weapon on the shard's surface.
List of appearances