Patient Predators. A face hugger spawns in an ovamorph and remains in a state of stasis until awakened by it's egg-shaped incubator. A creature within 10 feet of the ovamorph will awaken the face hugger within, (which in turn awakens any face hugger within 10 feet of that face hugger, potentially starting a chain reaction of face huggers awakening, which can open the ovamorph at any time as a free action. A face hugger remains invisible within the ovamorph until it lunges to attack. When a face hugger attacks from a hidden position (such as from within an ovamorph, creatures who are immune to surprise and have a readied action may attack the face hugger mid-leap as it exits the ovamorph. Otherwise, a face huggers' first attack from a hidden position is made with advantage.

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. 

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.

Leaping Attack. Melee Weapon Attack: +7 to hit, reach 5 ft., 1 target. Hit: 0 bludgeoning damage. When a face hugger makes a leaping attack, it leaps 10 feet as part of the attack. If the face hugger uses it's leap attack while hidden, it gains advantage on its attack roll. A creature hit by a face hugger's leaping attack is grappled and the face huger immediately use it's intubate ability as a reaction. Only creatures immune to surprise and who have a readied action may act as the face hugger as it emerges from hiding. 

Intubate. The face hugger makes a free attack: +7 to hit (with advantage) against a creature it has grappled. If the attack hits, the face hugger extrudes a tube down the victim's throat, wrapping it's eight spider-legs around the victims face and tail entwining the victim's neck. An intubated victim is incapacitated and reduced to zero hit points for as long as they are intubated. The face-hugger remains in this incubation process for 1d12 hours.

Removing a Face Hugger requires a medicine check DC 20 (at disadvantage if no specialized tools are used), but each attempt causes 11 (4d6) acid damage to the intubated host. If threatened, the face hugger attempts to asphyxiate the victim, who must roll a death save if they fail a DC 17 Constitution Saving Throw. Once a face hugger has completed its Incubation process on a victim, the face hugger releases the victim and dies.