Multiworm

Multiworm is a large, extradimensional worm in X-Com: Apocalypse.

Overview
Multiworm is an enormous, green worm with massive teeth and biting strength enough to sever a lightly protected limb. The creature is as large as a human is, if not slightly bulkier, and requires prodigious amount of food. It's most imporant mission is to feed as much as it can before it perishes. The worm isn't especially fast and can be outrun and it's clear they're not an attack unit.

It is unknown how long a multiworm is capable of surviving in our dimension, because naturally it never reaches that point. When it has provided enough nourishment for smaller worms it carries within it's bulk, four Hyperworms burst from the inside and quickly eat their carrier. This happens after a three day period.

Multiworms hatch from a bright pink egg that's crossed by purple veins. The eggs have a self defence mechanism and are capable of spitting acid at close ranges. The egg can detect human genome, so it is safe to assume that multiworm eggs are designed to be carried in to our dimension and develop self-reliantly into adult species. However, it is not uncommon to see other aliens such as Spitters guarding multiworm eggs.

Role in invasion
Multiworms are not built for warfare. They are a subversion element. That being said, they are immensely dangerous for unarmed civilians. Their most fearsome ability is to spit various enzymes at close range that can melt metal and dissolve organic matter. Maybe it uses this mixture to feed even faster, but replies to aggression with a gout of this lethal substance. Multiworm has no eyes, but can still launch it's attack with adequate accuracy, which suggests some other form of perception.

Multiworm eggs are laid by the Queenspawn in alien dimension, from where they are brought into our dimension during UFO incursions.