Tiny plant, lawful evil

Armor Class 17 (natural armor)
Hit Points 275 (50d4 + 150)
Speed 5 ft.

5 (–3) 14 (+2) 17 (+3) 21 (+5) 18 (+4) 15 (+2)

Saving Throws Con +9, Int +11, Wis +10
Damage Resistances acid, cold, fire, lightning
Damage Immunities poison
Condition Immunities blinded, charmed, deafened, exhaustion, frightened, paralyzed, poisoned, prone
Senses tremorsense 120 ft., blindsight 60 ft. (blind beyond this radius), passive Perception 14
Languages Common, Deep Speech, telepathy 120 ft.
Challenge 17 (18,000 XP)
Proficiency Bonus +6


  • Legendary Resistance (3/Day). If the sinstar fails a saving throw, it can choose to succeed instead.
  • Spiny Defense. A creature that touches the sinstar or hits it with a melee attack while within 5 feet of it takes 10 (3d6) piercing damage and, if the target is a Humanoid, it must succeed on a DC 19 Constitution saving throw or contract the thrall sickness disease (see the Thrall Sickness trait).
  • Thrall Sickness. A Humanoid infected with this disease manifests symptoms 1d4 days after infection, which include excessive thirst, increased desire for exposure to sunlight, and the appearance of itchy bumps on the skin. This disease wears down the victim’s psyche while slowly transforming its body. Until the disease is cured, at the end of each long rest, the infected creature must make a DC 19 Constitution saving throw. On a failure, the creature’s Dexterity and Intelligence scores are each reduced by 1d4. The reductions last until the infected creature finishes a long rest after the disease is cured. The infected creature dies if the disease reduces its Dexterity or Intelligence score to 0. A Humanoid that dies from this disease transforms into a star thrall under the complete psychic control of the sinstar that infected it. This otherworldly disease can be removed by the greater restoration spell or similar magic.


  • Multiattack. The sinstar uses Alluring Whispers. It then makes three Spines or Psychic Lash attacks.
  • Spines. Melee or Ranged Weapon Attack: +8 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 16 (4d6 + 2) piercing damage, and if the target is a Humanoid, it must succeed on a DC 19 Constitution saving throw or contract the thrall sickness disease (see the Thrall Sickness trait).
  • Psychic Lash. Ranged Spell Attack: +11 to hit, range 120 ft., one target. Hit: 18 (3d8 + 5) psychic damage.
  • Alluring Whispers. The sinstar telepathically whispers soothing and beckoning words in the minds of all Humanoids within 120 feet of it. Each target must succeed on a DC 19 Wisdom saving throw or be charmed for 1 minute. While charmed, a creature is incapacitated, and if it is more than 5 feet away from the sinstar, it must move on its turn toward the sinstar by the most direct route, trying to get within 5 feet of the sinstar and touch it. The creature doesn’t avoid opportunity attacks, but before moving into damaging terrain, such as lava or a pit, and whenever it takes damage from a source other than the sinstar, the creature can repeat the saving throw. A charmed creature can also repeat the saving throw at the end of each of its turns. If the saving throw is successful, the effect ends on it. A creature that successfully saves is immune to this sinstar’s Alluring Whispers for the next 24 hours.


The sinstar 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 sinstar regains spent legendary actions at the start of its turn.

  • Spines. The sinstar makes one Spines attack.
  • Teleport. The sinstar magically teleports up to 120 feet to an unoccupied space it can see.
  • Detonate Thrall (Costs 2 Actions). The sinstar orders one of its star thralls to explode. Each creature within 10 feet of the thrall must make a DC 19 Dexterity saving throw, taking 10 (3d6) bludgeoning and 7 (2d6) piercing damage on a failed save, or half as much damage on a successful one.


Sinstars lair on hills and on mountainsides below the treeline in most climate zones, eschewing only the coldest climes. Their lairs are identifiable by the multitude of eerily human-like cactuses that dot the nearby terrain.

On initiative count 20 (losing initiative ties), the sinstar takes a lair action to cause one of the following effects; the sinstar can’t use the same effect two rounds in a row:

  • Bolster Thrall. One star thrall the sinstar can see within 60 feet of it regains 10 (3d6) hp and has advantage on attack rolls until initiative count 20 on the next round.
  • Cactus Bloom. Small, spiny cactuses fill a 20-foot radius centered on a point on the ground the sinstar can see within 120 feet of it. That area becomes difficult terrain. When a creature that isn’t a star thrall moves into or within the area, it takes 7 (2d6) piercing damage for every 5 feet it travels. The cactuses wither away when the sinstar uses this lair action again or when the sinstar dies.
  • Choking Cloud. Nearby cactuses shed plumes of hairlike needles toward up to three creatures the sinstar can see within 60 feet of it. Each target must make a DC 19 Constitution saving throw or be incapacitated until the end of its next turn, as it coughs and chokes. A target within 5 feet of a star thrall has disadvantage on the saving throw.


The region containing a sinstar’s lair is altered by its otherworldly presence, which creates one or more of the following effects:

  • Aggressive Animals. Beasts within 1 mile of the sinstar’s lair behave erratically and attack Humanoids on sight.
  • Bitter Plants. Vegetation that grows within 1 mile of the sinstar’s lair tastes bitter and provides no sustenance to creatures that eat it.
  • False Lakes. There are no large bodies of water within 1 mile of the sinstar’s lair. Creatures discover that any major source of water they find is a mirage that fades away as soon as they approach within 20 feet of it.


This tiny cactus is covered in spines and dotted with star-shaped pink blooms. Vaguely human-shaped cactuses fill the area around the plant.

Sinstars originate from the far reaches between the stars, traveling to different worlds and planes as seed-spores encased in rocky shells. When their rocky vessels impact the surface of a plane, the spores are released, allowing them to take root if the conditions are right. Sinstars are startlingly intelligent, and their goal of assimilation often puts them at odds with their new home’s native life forms. Most sinstar scourges are destroyed before they get too large, but the prospect of a continent-sized infestation is truly terrifying.

Body Snatchers. Sinstars spread their influence by transforming humanoid victims into star thralls, their cactuslike servitors and guards. Star thralls are driven by the need to bring more humanoid victims to the sinstar, and some roam miles away from their sinstar parent to do so.

Section 15: Copyright Notice

Tome of Beasts 3 © 2022 Open Design LLC; Authors: Eytan Bernstein, Celeste Conowitch, Benjamin L. Eastman, Robert Fairbanks, Scott Gable, Basheer Ghouse, Richard Green, Jeremy Hochhalter, Jeff Lee, Christopher Lockey, Sarah Madsen, Ben Mcfarland, Jonathan Miley, Kelly Pawlik, Sebastian Rombach, Chelsea Steverson, Brian Suskind, Mike Welham

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