Acidic Blood. A Xendigo has a caustic blood like fluid that flows beneath its carapace.  A creature that deals bludgeoning, piercing, or slashing damage to the xenomorph while standing within 5 feet of it must make a DC 15 Dexterity saving throw, taking 18 (5d6) acid damage on a failed saving throw, or half as much acid damage on a successful one.  Additionally any creature that failed its save takes half as much damage on the following round.

Echolocation. The Xendigo can’t use its blindsight while deafened.

Pack Tactics. The Xendigo  has advantage on an attack roll against a creature if at least one of the Xenomorph’s allies is within 5 feet of the creature and the ally isn’t incapacitated.

Darkness Camouflage. The Xendigo has advantage on all Stealth checks when in Dim Light or Darkness

Frost Spray (Recharge 5-6). The Xendigo spits a sub zero fluid in a 20 foot cone, dealing 18 (5d6) points of cold damage to all creatures caught in the area.  Creatures can attempt a DC 15 Dexterity Saving throw for half damage.

Multiattack. A Xendigo makes two attacks: one with its Claws, one with its Bite.

Claws. Melee Weapon Attack: +5 to hit, reach 5 ft., 1 target. Hit:  7 (1d6 + 4) slashing damage. Any creature hit by the Xendigo's Claws must make a DC 14 Dexterity check or be grappled.

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., 1 target. Hit:  10 (1d8 + 6) Piercing and slashing damage. 

Proboscis. Melee Weapon Attack:  As a Bonus Action the Xendigo can extend a proboscis, complete with secondary jaws, to strike a Grappled creature.  This deals 10 (1d8+6) points of Piercing damage as well as 7 (2d6) points of Cold damage.  

Hunter's Rush. If a creature leaves the Xenomorph's threatened area the Xenomorph can move with it and make an attack with it's Tail.