Sand Trappers

While the Sand Trappers of Mars -the samller cousins of the Leviathan- surely look dangerous, one might think that they can be easily avoided since they are immobile... Wrong. These monsters wait under the sand until prey comes by, only to suddenly appear and grab it with its tentacles. And should the prey try to resist, it spits a paralysing venom at it. It can only effectively killed in a group.

Sadly, they can appear anywhere on the surface.

Lore
''These large, pod-like creatures would appear to be easily avoided -- they are completely immobile. Appearances can be deceiving, however. Like the Earth insect known as the ant lion (or more popularly, the doodlebug ) the sand trapper uses the lower portion of its abdomen as a shovel and digs itself a deep, conical pit in the loose sand of the plains. Any plantimal, worm, or human who gets too close loses its footing in the loose sand and falls to the bottom, where the creature waits to devour it. Even potential victims who don't fall within reach of the waiting creature have little chance of climbing out as the sand shifts beneath their feet. Escape is made even more difficult by the trapper's grasping, ropy tentacles.''