Entropy

gargantuan monstrosity, unaligned

Armor Class: 24 (Natural armor)

Hit Points: 997 ()

Speed: fly 80 ft (hover).

STR30(+10)DEX25(+7)CON25(+7)INT1(-5)WIS10(+0)CHA1(-5)

Saving Throws: Str +19, Dex +16, Con +16

Damage Resistances: acid, cold, fire, lightning, necrotic, poison, psychic, radiant, and thunder

Damage Immunities: bludgeoning, piercing, and slashing from nonmagical attacks

Condition Immunities: blinded, charmed, deafened, frightened, grappled, incapacitated, paralyzed, petrified, poisoned, prone, restrained, stunned, unconscious

Senses: blindsight 120 ft., passive Perception 10

Challenge: 30 (155,000 XP)

Immutable Presence: Entropy, the embodiment of chaos and primal force, defies the very laws that govern existence. Entropy is immune to any spell or effect that would alter its form. Additionally, Entropy cannot be moved, teleported, or banished against it's will.

Legendary Resistance (3/Day): If Entropy fails a saving throw, it can choose to succeed instead.

Chaos Shift: At the start of its turn, Entropy rolls . The first d8 determines a damage type that Entropy is immune to until the start of its next turn, as shown on the table below. The second d8 determines a damage type that Entropy is vulnerable to for the same duration, as shown on the same table. If Entropy rolls the same number for both d8s, it has no immunity or vulnerability for that turn.

d8	Damage Type
1	Acid
2	Cold
3	Fire
4	Force
5	Lightning
6	Necrotic
7	Poison
8	Radiant

Unusual Nature: Entropy doesn’t require air, food, drink, or sleep.

Spellcasting: Entropy can cast the following spells, requiring no material components:
At will: (self only)

Entropic Chaos: When a creature is damaged by one of Entropy's attacks or abilities, it takes 9 () damage of a random type and suffer a secondary effect, as determined by rolling on the table below. This includes legendary actions and lair actions.

d20	Damage Type	Secondary Effect
1	Acid	The target's armor or clothing is partially dissolved, reducing its AC by 1 until it is repaired or replaced.
2	Cold	The target is restrained by ice until the end of its next turn.
3	Fire	The target catches fire, taking 5 () fire damage at the start of each of its turns until it or another creature takes an action to extinguish the flames.
4	Force	The target is pushed 10 feet away from Entropy in a straight line.
5	Lightning	The target is stunned until the end of its next turn.
6	Necrotic	The target's maximum hit points are reduced by an amount equal to the damage taken. This reduction lasts until the target finishes a long rest.
7	Poison	The target is poisoned for 1 minute. It can repeat the saving throw at the end of each of its turns, ending the effect on a success.
8	Psychic	The target is confused for 1 minute. It must roll a d10 at the start of each of its turns to determine its behavior, as in the Confusion (enchantment) Level: 4 Casting Time: 1 action Concentration: Yes Ritual: No Creatures in a 10-ft-radius sphere must succeed on a Wis. save or can't take actions normally (+ 5-ft-radius/lvl). View on dndbeyond.com spell.
9	Radiant	The target is blinded for 1 minute. It can repeat the saving throw at the end of each of its turns, ending the effect on a success.
10	Thunder	The target is deafened for 1 minute. It can repeat the saving throw at the end of each of its turns, ending the effect on a success.
11	Slashing	The target bleeds profusely, taking 5 () slashing damage at the start of each of its turns until it receives magical healing or a DC 15 Medicine check.
12	Piercing	The target is impaled by a shard of metal or bone, reducing its speed by 10 feet until it or another creature takes an action to remove the shard.
13	Bludgeoning	The target is knocked prone.
14	Force	The target's size increases or decreases by one category (Entropy's choice) for 1 minute.
15	Psychic	The target ages forward or backward (Entropy's choice) by years. This has no effect on the target's statistics, but may alter its appearance.
16	Force	The target becomes unaffected by gravity for 1 minute. During this time, the target can move only by pushing or pulling against a fixed object or surface within reach (such as a wall or a ceiling), which allows it to move as if it were climbing.
17	Psychic	The target sees a horrific illusion of its worst fear for 1 minute. It is frightened of Entropy for the duration.
18	None	The target is charmed by Entropy for 1 minute. It regards Entropy as a friend and will not harm it or its allies. It can repeat the saving throw at the end of each of its turns, ending the effect on a success.
19	None	The target is polymorphed into a sheep for 1 minute. It retains its personality and alignment, but its statistics are replaced by those of a sheep. It can repeat the saving throw at the end of each of its turns, ending the effect on a success.
20	None	The target rolls on the Wild Magic Surge table to determine a random magical effect.

Actions

Multiattack: Entropy makes three attacks: one with its pseudopod, one with its chaos bolt volley, and one with its chaos blast.

Pseudopod: Melee Weapon Attack: +17 to hit, reach 15 ft., one target. Hit: 32 () bludgeoning damage plus 14 () damage of the type Entropy is immune to on this turn, or force if Entropy has no immunities.

Chaos Bolt Volley: Entropy chooses up to 5 () creatures within 120 feet of it that it can see. Each creature must make a DC 22 Dexterity saving throw or be hit by a spell as if cast by Entropy at 9th level.

Chaos Blast (Recharge 5-6): Entropy unleashes a blast of chaotic energy in a 60-foot cone. Each creature in that area must make a DC 22 Wisdom saving throw, taking 56 () damage on a failed save, or half as much damage on a successful one. The damage type is the same as the damage type Entropy is immune to on this turn, or force if Entropy has no immunities.

Legendary Actions

Entropy can take 3 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. Entropy regains spent legendary actions at the start of its turn.

Pseudopod: Entropy makes one pseudopod attack.

Move: Entropy moves up to it's speed without provoking opportunity attacks.

Chaos Shift (Costs 3 Actions): Entropy teleports up to 120 feet to an unoccupied space that it can see. It can then use its chaos blast without recharging.

Lair Actions

Entropy does not have a fixed lair, but rather considers any area within 1 mile of its presence as its domain.
On initiative count 20 (losing initiative ties), Entropy can take a lair action to cause one of the following effects; Entropy can’t use the same effect two rounds in a row:

Sphere of Chaos: Entropy creates a 20-foot-radius sphere of chaotic energy at a point it can see within 120 feet of it. The sphere lasts until the start of Entropy’s next turn. Any creature that enters the sphere or starts its turn there takes 1 force damage. (This triggers Entropic Chaos)

Random Debris: Entropy causes a 60-foot-radius area within 120 feet of it to become difficult terrain. The terrain is filled with random obstacles, such as sticky honey, spikes, scattered furniture, pits, webs, or other obstacles. The effect lasts until the start of Entropy’s next turn.

Chaotic Interference: Entropy causes a 60-foot-radius area within 120 feet of it to become distorted by chaotic magic. Any creature in the area must make a DC 22 Intelligence saving throw or have disadvantage on attack rolls, ability checks, and saving throws until the start of Entropy’s next turn.

True Polymorph: Entropy chooses one creature within 120 feet of it that it can see. The creature must make a DC 22 Wisdom saving throw or be affected by the spell as if cast by Entropy at 9th level. The effect lasts until the next lair action is triggered. The creature is transformed into a random object or creature, as determined by rolling on the table below.

d100	Object or Creature
01-02	A young red dragon
03-04	A blink dog
05-06	A harpy
07-08	A wooden chair
09-10	A bugbear
11-12	A mind flayer
13-14	A cat
15-16	A goblin
17-18	A fire giant
19-20	A gelatinous cube
21-22	A kobold
23-24	A vampire
25-26	A troll
27-28	A griffon
29-30	A rubber duck
31-32	An adult gold dragon
33-34	A beholder
35-36	A demilich
37-38	A mimic
39-40	A sperm whale
41-42	A bowl of petunias
43-44	A hobgoblin
45-46	A unicorn
47-48	A centaur
49-50	A pixie

d100	Object or Creature
51-52	A dog
53-54	A merfolk
55-56	A medusa
57-58	A minotaur
59-60	A hydra
61-62	A nightwalker
63-64	A cyclops
65-66	A cloud giant
67-68	A purple worm
69-70	A skeleton
71-72	A zombie
73-74	A mummy
75-76	An animated armor
77-78	A roc
79-80	A banshee
81-82	A death knight
83-84	A chimera
85-86	A young bronze dragon
87-88	A remorhaz
89-90	A bulette
91-92	A rat
93-94	A dryad
95-96	A wolf
97-98	A gnoll
99-00	A flumph

Note: This list contains monsters up to CR20. This means it will only work for parties with level 20 players. If the player characters are lower than level 20, you may need to make some adjustments to this list, or ignore the limitations of the True Polymorph (transmutation)
Level: 9
Casting Time: 1 action
Concentration: Yes
Ritual: No
Transform a creature or object into a new form (creature <-> object). The new form can be permanent.
View on dndbeyond.com spell.

Regional Effects

The region containing Entropy’s lair is warped by its presence, creating one or more of the following effects:
If Entropy is destroyed or leaves the plane, these effects end immediately.

Weather: The weather in the region is unpredictable and extreme, changing from calm to stormy, hot to cold, or day to night in a matter of minutes.

Terrain: The terrain in the region is unstable and shifting, creating sinkholes, fissures, or mounds of rubble at random locations.

Magic: The magic in the region is unstable and wild, causing spells and magical items to malfunction or produce random effects. Whenever a creature casts a spell or uses a magical item within 1 mile of the lair, the DM can roll on the Wild Magic Surge table to determine a random magical effect.

Notes

Entropy is a terrifying creature that defies all logic and order. It is a shapeless mass of chaotic energy that constantly changes its form, color, and texture. It has no discernible features, except for a single, vortex like maw that devours anything that comes in it's way. Entropy is not a living being, but a manifestation of the Elemental Chaos, the primal force that opposes the order of Mechanus. It has no mind, no purpose, and no allegiance, only a hunger for destruction and disorder. It can warp reality around it, creating random effects that defy logic and physics. It's immunities and resistances constantly shift, making it even more unpredictable in combat.
Entropy has the innate ability to cast plane shift at will, without any material components. This allows it to travel across the multiverse, appearing and disappearing in different planes of existence. Entropy does not use this ability to seek out specific destinations or to escape from danger. It simply moves randomly, following its chaotic nature. Entropy does not care where it goes, as long as it can cause destruction and disorder. Whenever Entropy arrives in a new plane, it unleashes its chaotic energy, disrupting the natural laws and creatures of that plane. It does not stay long, however, as it soon grows bored and shifts to another plane. Entropy’s movements are unpredictable and erratic, making it hard to track or anticipate. No one knows where Entropy will appear next, or what havoc it will cause.
Entropy is a highly dangerous and unpredictable foe. It does not communicate or negotiate, but attacks anything that comes near it. It does not have a strategy or a tactic, but relies on its chaos aura and chaos blast to wreak havoc on its enemies. It does not fear death or pain, but enjoys the chaos and suffering it causes. It does not have a lair or a territory, but wanders the world randomly, leaving a trail of devastation behind it. Entropy is a force of nature, a cosmic anomaly, and a threat to all existence.
Entropy does not have a fixed lair, but rather considers any area within 1 mile of its presence as its domain. Wherever it goes, it leaves a trail of chaos and devastation behind. The region containing Entropy’s domain is warped by its presence.
Entropy has never been to Mechanus, the plane of ultimate order and law, where everything operates with clockwork precision and logic. Mechanus is the antithesis of Entropy, and the two forces would react unpredictably if they ever met. No one knows what would happen, but it would probably be very bad. However, for some unknown reason, Entropy has never entered Mechanus, despite its random movements. Some speculate that there is a hidden law or pattern that governs Entropy’s movements, preventing it from reaching Mechanus. Others believe that Mechanus has a powerful defense mechanism that repels Entropy’s chaotic energy. Whatever the reason, the multiverse is safer for it, as the collision between Entropy and Mechanus would be a cosmic catastrophe, threatening the very fabric of reality.
If Entropy is reduced to 0 hit points, it does not die. Instead, it vanishes in a burst of chaotic energy and reappears in a random location in the multiverse after × days. The location is determined by the DM, or by rolling on the table below. Entropy has no control over where it reappears. Entropy regains all its hit points and abilities when it reappears.

d100	Plane
01-05	Abyss
06-10	Acheron
11-15	Arborea
16-20	Arcadia
21-25	Beastlands
26-30	Bytopia
31-35	Carceri
36-40	Elysium
41-45	Gehenna
46-50	Gray Waste
51-55	Limbo
56-60	Shadowfell
61-65	Mount Celestia
66-70	Outlands
71-75	Pandemonium
76-80	Sigil
81-85	Ysgard
86-90	Material Plane
91-95	Feywild
96-00	The Far Realm