Rockworms

Rock worms are the most dangerous enemies encountered in the underground of Mars.

Description
Not only have these worms grown to huge size, they are also very fast, heavily armoured and can kill a lesser man with one bite. Even worse, their skin is coated with acid! Their size is likely due to their habit of making their homes near the element, radium, which makes it unfortunately difficult to acquire. When they sense intruders, they shoot out of the tubes the live in to greet them properly - with death.