Lanky

Lankies, also called Big Uglies, are a species of gigantic and hostile aliens that began attacking human colony worlds in 2111, killing their inhabitants and terraforming them into more Lanky-friendly environments. They are the main antagonists of Marko Kloos' Frontlines series.

Anatomy & Physiology
Lankies are incredibly large creatures, rivaling the largest Earth animals in size and far surpassing them in weight. Lankies average 80 feet (25 m) in height on all fours, with a 30% size variation that can lead to heights between 65 feet (20 m) and 100 feet (30 m). They seem to be denser than Earth animals, weighing a few hundred tons on average, and were originally believed to weigh 1,100 tons (1,000 metric tons) based on incorrect battlefield estimates. In any case, their mass is so great that the earth literally shakes under their steps.

As their name implies, Lankies are quite thin. They are quadrupeds, with very long forelimbs and short hindlimbs ending in three-toed feet. Their stance is therefore similar to that of Death Angels or the Cloverfield Monster. The head has no eyes and has a shield-shaped plate on top. Their skin is gray or eggshell-white in color and extremely tough, allowing Lankies to shrug off heavy gunfire. Their mouths are not described, but they presumably have them, as they make loud vocalizations when injured.

Environment
Lankies thrive in atmospheres quite different to that of Earth. Their preferred atmosphere seems to be roughly 80% nitrogen and 20% carbon dioxide, with only trace quantities of oxygen. Despite this, they are able to function in Earth-like atmospheres, although possibly at reduced ability.

Senses
Despite their lack of eyes, Lankies are apparently able to see, as sufficiently advanced visual camouflage appears to work against them. They are also able to sense radio, implying that they may use radio waves to navigate.