Gryllus Swarm

Large swarm of Tiny Constructs, lawful neutral

Armor Class 15 (natural armor)
Hit Points 110 (17d10 + 17)
Speed 30 ft.

14 (+2) 18 (+4) 13 (+1) 6 (–2) 13 (+1) 10 (+0)

Skills Insight +4, Perception +4
Damage Vulnerabilities acid, fire
Damage Resistances bludgeoning, piercing, slashing
Damage Immunities poison, psychic
Condition Immunities charmed, exhaustion, frightened, grappled, paralyzed, petrified, poisoned, prone, restrained, stunned
Senses darkvision 60 ft., passive Perception 14
Languages understands the languages of its creature but can’t speak
Challenge 6 (2,300 XP)
Proficiency Bonus +3


  • Book Bound. The swarm’s hp maximum is reduced by 1 for every minute it is further than 60 feet from its book. When its hp maximum reaches 0, it dies. If the swarm’s book is destroyed or moved to another plane of existence separate from the swarm, the swarm must succeed on a DC 11 Constitution saving throw or be reduced to 10 hp. The swarm can bind itself to a new book by spending a short rest in contact with the new book.
  • Construct Nature. The swarm of gryllus doesn’t require air, food, drink, or sleep.
  • Immutable Form. The swarm is immune to any spell or effect that would alter its form.
  • In the Margins. The swarm can spend half its movement to enter or exit its book. While inside its book the swarm is indistinguishable from illustrations on a page.
  • Swarm. The swarm can occupy another creature’s space and vice versa, and the swarm can move through any opening large enough for a Tiny construct. The swarm can’t regain hp or gain temporary hp.


  • Multiattack. The swarm of gryllus makes two Go for the Knees or Go for the Eyes attacks. It can replace one attack with a use of Timber.
  • Go for the Knees. Melee Weapon Attack: +7 to hit, reach 0 ft., one target in the swarm’s space. Hit: 18 (4d8) slashing damage, or 8 (2d4 + 3) slashing damage if the swarm has half of its hp or fewer. The target must succeed on a DC 15 Constitution saving throw or its speed is reduced by 10 feet until the end of its next turn.
  • Go for the Eyes. Ranged Weapon Attack: +7 to hit, range 20/60 ft., one target. Hit: 18 (4d8) piercing damage, or 8 (2d4 + 3) piercing damage if the swarm has half of its hp or fewer. The target must succeed on a DC 15 Wisdom saving throw or be blinded until the end of its next turn.
  • Timber. The swarm calls out in synchronous, tiny voices before chopping away at the feet of one creature in the swarm’s space. The target must succeed on a DC 15 Strength saving throw or be forced prone. If the target is forced prone, the swarm can then make one Go for the Knees attack against it as a bonus action.


The forgotten tome cracked open and out sprang a throng of tiny, colorful people; illustrations come to life.

Gryllus, also known as marginites, are manuscript illustrations brought to life through transmutation rituals. A singular gryllus is little more than a tiny armless humanoid with a costume and prop, often a caricature of a profession, such as baker or guard.

But an entire tome’s worth of gryllus forms a teeming swarm with a unified purpose, usually a compulsion to defend the book where they are found.

Secret Guardians. Wizards and other masters of arcana create swarms of gryllus to protect their precious spellbooks and esoterica. Religious and secret orders who lack the knowledge of their creation pay handsomely to have holy texts embellished with gryllus protection. Swarms of gryllus created this way often judge their book’s readers, praising the worthy and annoying any undesirables who browse through their pages.

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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