Brood Sovereign of the Thousand Monsters

Hive Sovereign
The Brood Sovereign can control any creature it spawns telepathically within 1 mile. Spawned creatures act immediately after the Sovereign in initiative.

Endless Gestation
At the start of each of the Sovereign’s turns, it spawns one Broodling in an unoccupied space within 30 feet.
If the Sovereign takes 40 or more damage in a single turn, it spawns two Broodlings instead at the start of its next turn.
If reduced below half its hit points, it instead spawns one Greater Spawn every other turn.
There is no limit to the number of creatures it can spawn.

Brood-Fueled Vitality
When a spawned creature dies within 60 feet of the Sovereign, the Sovereign regains 15 hit points.

Monstrous Anchor
The Sovereign has advantage on saving throws against spells or effects that would move it or knock it prone.

Multiattack

The Sovereign makes three attacks: two with its Rend and one with Devouring Maw.

Rend

Melee Weapon Attack: +14 to hit, reach 15 ft., one target.

Hit: 25 (3d10 + 8) slashing damage plus 10 (3d6) acid damage.

Devouring Maw

Melee Weapon Attack: +14 to hit, reach 10 ft., one target.

Hit: 30 (4d10 + 8) piercing damage. If the target is Large or smaller, it must succeed on a DC 20 Strength save or be swallowed.

A swallowed creature takes 21 (6d6) acid damage at the start of each of the Sovereign’s turns. If the Sovereign takes 40 damage in a single turn, it must succeed on a DC 20 Con save or regurgitate all swallowed creatures.

Birthing Cataclysm (Recharge 5–6)

The Sovereign violently ruptures reality. It immediately spawns 1d4+1 Broodlings and one Greater Spawn in spaces within 60 feet. Creatures of the Sovereign’s choice within 20 feet of each spawned creature must succeed on a DC 20 Dex save or take 14 (4d6) acid damage.

Legendary Actions (3/round)

Spawn Surge (Costs 2 Actions). The Sovereign spawns one Broodling.

Psychic Command. One spawned creature immediately makes one attack.

Thrashing Bulk. The Sovereign makes one Rend attack.