Acidic Blood. A Xenomorph's blood is composed of powerful acid. Any melee attack against a xenomorph sprays acid blood from the wound, dealing 11 (4d6) acid damage to the attacker and any items or creatures in the xenomorph's space as well as to anyone grappling or grappled by the xenomorph. Ranged attacks cause damage only to objects and creatures in the xenomorph's space. Creatures that succeed in a DC 16 Dexterity Saving throw avoid the damage. 

Murderous Symbiote. A chestburster will burst from its host body 4 (1d10-1) hours after a xenomorph facehugger has completed it's intubation process. In occasional misfortunate circumstances, a chestburster will emerge immediately upon completion of the intubation process. When a chestburster emerges, its host is immediately reduced to zero hp and suffers a failed death saving throw prior to making any death saves on subsequent rounds. Subsequent death saving throws suffer disadvantage. If not threatened when it emerges, it will devour it's host body, leaving behind a skeletal body devoid of soft tissues, dripping with acidic saliva. In a hive, the bodies of the dead are left to be subsumed into the walls, floors or ceilings of the chitinous framework of the hive structure.

Molt. A chestburster will molt into a xenomorph drone or runner in 1d4 days from emerging from its symbiote host; small and smaller creatures become runners, medium creatures become drones. This change can be accelerated by one day for each creature the chestburster consumes. The metamorphosis takes one hour, during which time the chestburster is incapacitated.

Hive Mind and Ecology. Xenomorphs communicate telepathically and through pheromones. A hive must have a queen. When multiple hives exist in a world, the world must have an empress to keep the hives from consuming one another. Queens serve the xenomorph empress under compulsion unless the empress shows a sign of weakness, which prompts the queen/s to slay the empress who feast on its corpse and molt to become the next empress. Each planet may only host one empress. Telepathic communication between xenomorphs is conveyed only with intent, urge, and hate for all other creatures. Xenomorphs unerringly follow the imperatives of their queen (queens follow the imperatives of the empress). On the rare occasion that a royal facehugger/chestburster spawns from an ovomorph, the hive conceals and hides the embryonic xenomorph until such time as it can morph into a new queen, prompting a deathmatch for rulership of the hive and retaining only the strongest xenomorph queens.

A Chestburster may make a single leaping attack against an enemy it believes it can kill in a single attack. Otherwise, chestbursters prime imperative is to flee and escape detection until it singles off a suitable target, typically seeking out vermin or pets for it's first meal. 

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., 1 target. Hit: 1 (1d6-3) slashing damage. 

Leap. The chestburster leaps up to 30 feet as a bonus action. The movement does not provoke opportunity attacks.