The starfish leviathan
Deep below the crater into which the Cicada crashed, the very crater from which we escaped in our life pod, something lurks.
The Starfish Leviathan is a massive creature resembling a starfish. It primarily feeds on metals, dissolving them from the seabed with powerful acids. Even precious metals pose no challenge to it. In addition, it feeds on organic remains such as carcasses or decaying plant matter that sink to the floor of the crater.
The excess metals are stored within its exoskeleton, making it nearly impervious to external damage. By dissolving the ground beneath it, the creature burrows ever deeper and follows rich ore veins through the planet’s crust.
Anyone approaching the Starfish Leviathan while carrying metal objects, or worse, traveling inside a submarine, will attract its attention. It will stretch its arms toward the metal, using countless suction cups to seize and consume it. Any humans trapped inside the vehicle are merely a welcome bonus.
Those who manage to slip past it will reach the Khaara Root Network Caves. There, the Kharaa bacterium has infected the roots of the World Tree and is spreading through the underground root system. By following the corrupted roots deeper below, we eventually enter a chamber containing an infected Collector Leviathan that is slowly merging with the root network itself.
The Kharaa pathogen is exploiting the advanced brains of the Leviathans in order to develop strategies for its own spread.