The Multiworm resembles a large green worm with teeth that spits acid. This is one of the earliest units you will meet. It is one of the most valuable Biochemistry research specimens, and it is therefore recommended that one be captured early.
The Multiworm is a low ground hugging creature that spans across two tiles and has moderate armor coupled with a high amount of health. This makes it difficult to kill with early low powered weaponry. The high health also requires that it has to be carefully injured before it can be stunned.
The acid attack is similar to a Spitters attack but is much more vicious due to its rapid-fire nature. It can do low to moderate damage and this can result in heavy damage even to the best protected agents.
When a Multiworm is killed, four Hyperworms will burst from its corpse. These can be more dangerous than the Multiworm itself, especially in turn-based mode as they spawn with high TUs and enough reaction time to wound or kill agents. It is recommended that you deal some stun damage with Stun Grenades or a Stun Grapple so that the Multiworm can be knocked unconscious rather than killed. If a Hyperwom is killed, saturate the area with explosives to quickly kill its spawn.
Some Multiworms towards the late game may have less than 4 Hyperworms or none at all. There is also an AI bug where they will shoot at a flying agent despite being barely out of range.
Official Entry (Captured Alive): "The Multiworm is clearly a crucial stage in the complex Alien life cycle. It is capable of attacking by propelling a fluid from pores along the side of the body containing a complex mix of micro-organisms that use enzymes and acids to break down the molecular structure of the target. Fortunately the range of the propellant is fairly short. The Multiworm is slow moving, but care should be taken in combat because it may release its offspring in the throes of death, creating an even greater threat."
Official Entry (Autopsy): "This creature is a rapacious carnivore whose feeding frenzy contributes to the rapid growth of younger lifeforms called "Hyperworms" which are reared inside its body. The gestation period for the Hyperworms is about three days and each Multiworm gives birth to four offspring. The birth process is lethal for the parent - the Hyperworms explode from the Multiworms body and consume it within a matter of seconds. The brain structure of the Multiworm is undeveloped and it is unlikely to be affected by Psionic attacks. The tissue analysis from the autopsy will provide an invaluable contribution to our biological warfare research."