Once the Face-hugger has altered the victim's genetic code, the host body starts to rapidly create the xenomorph embryo. During this time, the victim's immune system strengthens (providing a bonus of +20 to Biological, Chemical, and Poison SMRs), in addition to his physical Strength (+20). The host's metabolism increases (+10 Agility) and he becomes more resistant to pain (+20 SMR). The amount of time required for the embryo to develop is based on several factors, but for convenience, say it takes 3D10 hours.

The appearance of a Chestburster will vary from incident to incident. They are usually just under half-a-meter long, flesh colored, and covered in blood. Sometimes the mouth and arms will already be partially developed, other times, not. Since the embryo is developed from the host's DNA, it will often have some characteristics of the host. The xeno has a 40% chance to have any unusual physical abilities possessed by the host.

When the embryo is ready to emerge, the host will feel an intense pain in his chest/torso, caused by the baby ramming and chewing it's way through the sternum. The emergence takes 2D6x10 seconds to complete. The host's chest will begin to bleed and bulge outwards ( Roll a Mental SMR or be stunned into inaction for 2D4 seconds ). The Chestburster will breakthrough, with a spray of gore, and scream. The victim must roll a System Shock test. If successful, he will live for 2D6 seconds. During this time, Zen or technological healing may be applied. If the System Shock roll fails, the victim dies immediately.

With surprising speed ( and a -8 initiative bonus ), the Chestburster will vacate the host body and begin searching for a place to hide and develop. Once the Chestburster finds a secure hiding place, it will begin to develop into an adult. This takes 1D12 hours, during which time the bug will shed it's skin 1-2 times.

The Chestburster has Climbing 6, Stealth 8.

The Chestburster is found in the same place as the Face-hugger.