Sea spiders were amphibious Rahi that first appeared off Ga-Metru after the Visorak invasion. As the Rahaga quickly discovered, sea spiders were a natural predator of Visorak, one of the only ones known. Sea spider venom shrunk its prey to a more manageable size. The creature then cast its target into stasis using its spinner. Sea spiders were never spotted anywhere on or around Mata Nui.1
Notes
This arachnid was actually an amphibious creature of the sea and was the only known natural predator of the Visorak. While not large enough to pose a threat to a Visorak one-on-one, the front legs of a sea spider were able to inject venom that shrank its foe down to a more manageable size. Sea Spider spinners could then throw prey into temporary stasis until such time as the hunter was ready to feed. Sea Spiders did not hunt in groups and were actually hostile to each other.2
Sea spiders were first spotted in Metru Nui after the arrival of the Visorak, in the sea off Ga-Metru. According to the Rahaga, the sea spider was a natural enemy of the Visorak, and large numbers of them followed the hordes from place to place. They spent most of their time in the water, where they were safe from all Visorak breeds except the Boggarak. Sea spiders hunted by surprising their prey, then injecting venom using their forelegs. The venom physically shrunk a target to a more manageable size. The sea spider then used its spinner to put its prey into stasis until such time as it was ready to feed. Unlike the Visorak, sea spiders did not hunt in large groups. In fact, members of this species seemed to hate each other actively. Visorak were at times saved when another sea spider intervened to disrupt another's hunt. Sea spiders had no nests, colonies, or any kind of organized leadership. They would not cooperate even in life-or-death situations. This limited their success against the Visorak.3
According to Rahaga Gaaki, sea spiders were one of the only Rahi she did not try to capture, since they were a threat to the Visorak. She remarked that if she needed to defeat one, she would simply lure two of them together and let them fight each other. The only thing she ever saw a sea spider back away from was, strangely, a Bohrok Krana in a display case in the Archives.3