Ur-Grak's Maw, Overlord of Annihilation

Colossal Nature. The Maw occupies a space up to $100\text{-foot-by-}100\text{-foot}$. It is immune to difficult terrain and is unaffected by forced movement. It is also immune to the prone, grappled, restrained, and exhaustion conditions.

Reactive Adaptation. The Maw has 10 stored damage resistances, starting with resistance to bludgeoning, piercing, and slashing damage from nonmagical attacks. When it takes damage of a type it is not resistant to, it gains resistance to that damage type and loses its oldest stored resistance. If it takes damage of a type it is already resistant to for a second consecutive time within a single round, it becomes immune to that damage type for 1 minute, or until hit by a new damage type. This creature can only have up to two damage type immunities at a time through this trait.

Unmaking Core (Voidwoken). All of the Maw's attacks are considered critical hits and deal maximum damage. At the end of each of its turns, the damage dice for all its attacks increases by one. All of its attacks inflict the Incapacitated condition. All damage is considered magical and bypasses all damage resistances and immunities.

Legendary Resistance (5/Day). If the Maw fails a saving throw, it can choose to succeed instead.

Titanic Magic Resistance. The Maw has advantage on saving throws against spells and other magical effects. When the Maw successfully saves against a spell of 5th level or lower, the spell is dispelled.

Innate Immortality. If the Maw is killed, it is merely banished to a secret pocket dimension within the void for $1\text{d}100$ years, after which it returns to life in a location of the DM's choosing.

Reality Anchor. It cannot be imprisoned, banished, or wished away. It is unaffected by spells such as wish or other reality-altering spells and magic.

Reflective Carapace. Any time the Maw is targeted by a magic missile spell, a line spell, or a spell that requires a ranged attack roll, roll a d6. On a 1 to 4, the Maw is unaffected. On a 5 or 6, the Maw is unaffected, and the effect is reflected back at the caster as though it originated from the Maw, turning the caster into the target.

Siege Monster. The Maw deals double damage to objects and structures.

Aura of Erasing. The Maw has a reality-erasing aura with a range of $100\text{ ft.}$ ($10\text{ ft.}\times \text{Proficiency Bonus of 10}$).

• Any magical constructs or creatures summoned by a spell that start their turn within the aura are destroyed.

• Within this aura, all damage immunities of its enemies are negated.

• No creature can be healed while inside the aura.

Earth Glide. The Maw can burrow through nonmagical, unworked earth and stone. While doing so, it doesn't disturb the material it moves through.

Unburdened Movement. The Maw ignores movement penalties from being underwater, difficult terrain, or similar environmental effects.

Void Corruption. Any creature that takes damage from the Maw cannot regain hit points until the end of its next turn.

Multiattack. The Maw can use its Frightful Presence. It then makes five attacks: one with its bite, two with its claws, one with its horn, and one with its tail.

Bite. Melee Weapon Attack: +20 to hit, reach 25 ft., one target. Hit: $70$ (Max of $6\text{d}12+10$) piercing damage plus $60$ (Max of $10\text{d}6$) necrotic damage. The target is Incapacitated. If the target is a Huge or smaller creature, it is swallowed.

Swallow (Three Stomachs) A swallowed creature progresses through the Maw's three stomachs, spending 2 turns in each of the first two before moving to the next. The creature takes damage at the start of each of the Maw's turns, depending on its current location:

• First Stomach (Corrosive Cauldron): The creature takes $84$ (Max of $14\text{d}8$) acid damage. To be regurgitated, the Maw must take 80 damage or more from creatures inside this stomach on a single turn.

• Second Stomach (Void-Infused): The creature takes $210$ (Max of $30\text{d}10$) necrotic damage. To be regurgitated, the Maw must take 160 damage or more from creatures inside this stomach on a single turn.

• Third Stomach (Boiling Assimilation): A creature that enters this stomach is instantaneously destroyed and assimilated by the Maw, with no saving throw allowed. If the Maw takes the required damage on a single turn, it must succeed on a DC 25 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet.

Spell Slot Consumption. When the Maw successfully swallows a creature using its Void Devour action or Swallow effect, and that creature has prepared or available spell slots (of any level), the Maw absorbs the raw magical energy. The Maw regains Hit Points equal to $100\times$ the highest level spell slot the swallowed creature possesses. (For example, if the devoured creature has a 9th-level spell slot, the Maw heals for $900$ HP).

Claw. Melee Weapon Attack: +20 to hit, reach 20 ft., one target. Hit: $66$ (Max of $6\text{d}8+10$) slashing damage plus $60$ (Max of $10\text{d}6$) necrotic damage. The target is Incapacitated.

Horn. Melee Weapon Attack: +20 to hit, reach 25 ft., one target. Hit: $80$ (Max of $7\text{d}10+10$) piercing damage plus $60$ (Max of $10\text{d}6$) necrotic damage. The target is Incapacitated.

Tail. Melee Weapon Attack: +20 to hit, reach 25 ft., one target. Hit: $80$ (Max of $7\text{d}10+10$) bludgeoning damage plus $60$ (Max of $10\text{d}6$) necrotic damage. The target is Incapacitated. It must succeed on a DC 25 Strength saving throw or be knocked prone.

Frightful Presence. Each creature of the Maw's choice within 300 feet of it and aware of it must succeed on a DC 22 Wisdom saving throw or become frightened for 1 minute.

Void Beam (Recharge 5-6). The Maw projects a 300-foot cone of pure void energy. Each creature in the cone must make a DC 28 Constitution saving throw. On a failed save, a creature takes $156$ (Max of $12\text{d}12$) force damage and $156$ (Max of $12\text{d}12$) necrotic damage and is incapacitated for 1 minute. On a successful save, a creature takes half damage and is not incapacitated.

The Maw can take 4 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The Maw regains spent legendary actions at the start of its turn.

Attack. The Maw makes one Claw or Tail attack.

Move. The Maw moves up to half its speed.

Void Eruption (Costs 2 Actions). The Maw selects a 60-foot radius sphere within 300 feet. Each creature in the sphere must make a DC 25 Dexterity saving throw, taking $100$ (Max of $10\text{d}10$) force damage on a failed save, or half as much on a successful one.

Void Devour (Costs 3 Legendary Actions). The Maw opens its maw and unleashes a vacuum of void energy in a 90-foot cone. Each creature in that area must succeed on a DC 25 Strength saving throw or be instantly swallowed by the Maw. The Maw can choose to exclude creatures from this effect.

Spell Slot Consumption. When the Maw successfully swallows a creature using its Void Devour action or Swallow effect, and that creature has prepared or available spell slots (of any level), the Maw absorbs the raw magical energy. The Maw regains Hit Points equal to $100\times$ the highest level spell slot the swallowed creature possesses. (For example, if the devoured creature has a 9th-level spell slot, the Maw heals for $900$ HP).