Acidic Blood. Any nonmagical weapon made of metal that hits the Monarch Queen corrodes. After dealing damage, the weapon takes a permanent and cumulative -1 penalty to  damage rolls. If its penalty drops to -5, the weapon is destroyed. Nonmagical ammunition made of metal that hits the Monarch Queen is destroyed after dealing damage. Whenever the Monarch Queen takes physical damage, any other creature within 5 feet of it must succeed on a DC 15 Dexterity saving throw or take 5 (1d8) acid damage

Hive Mind. The Monarch Queen can communicate and coordinate with all Xeno type monstrosities regardless of distance.

Spider Climb. The Monarch Queen can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Night Stalker. The Monarch Queen has advantage on stealth rolls in dim lighting and total darkness.

Grappler. When the Monarch Queen lands an attack with her claws on a target, she can attempt to grapple the target as a bonus action. If the target is grappled, it can use an action on its turn to attempt to escape DC 20 STR or DEX.

Egg Laying. The Monarch Queen can lay 1d6 Eggs per hour. Eggs reach maturity in 7 days at which point they become active, containing an Face Hugger.

Legendary Resistance (3/day).  If the Monarch Queen fails a saving throw, it can choose to succeed instead.

Multiattack. The Monarch Queen can make 3 Claw attacks or 1 Claw and either 1 Tail Spear or Little Mouth. 

Claw. Melee Weapon Attack: +14 to hit, reach 10 ft., one. Hit: 22 (3d8+8) slashing damage

Little Mouth. Melee Weapon Attack: +14 to hit, target must be grappled by the Monarch Queen, one. Hit: 39 (8d6+8) piercing damage. and 32 (8d6) acid damage.

Tail Spear. Melee Weapon Attack: +14 to hit, reach 10 ft., one. Hit: 49 (7d10+8) piercing damage.

Freighting Presence. The Monarch Queen shrieks. Each creature of her choice that is within 120ft of her must succeed on a DC 20 WIS saving throw or become frightened for 1 minute. The creature can repeat the savings throw at the end of each of its turns. Once a creature has successfully passed the saving throw it is immune to the Monarch Queen's Freighting Presence for the next 24 hours.

The Monarch Queen can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. The Monarch Queen regains spent legendary actions at the start of its turn.

Claw. 1 Action.

Tail Swipe. 1 Action. The Monarch Queen makes one Tail Spear attack. On a hit the target must make a DC 20 DEX saving throw or be knocked prone.

Regroup. 2 Actions. The Monarch Queen immediately makes a move action that does not provoke opportunity attacks. All Xenomorphs that the Monarch Queen ends this movement next to gain temporary hit points equal to their CR rating.