Urchin Swarm, Ravenous

Medium swarm of Tiny beasts, unaligned

Armor Class 13
Hit Points 72 (16d8)
Speed 0 ft., swim 20 ft.

1 (-5) 12 (+1) 10 (+0) 4 (-3) 13 (+1) 9 (-1)

Senses passive Perception 11
Challenge 1 (200 XP)

Special Traits

  • Jet. While underwater, a ravenous urchin swarm can Dash as a bonus action and does not provoke opportunity attacks while jetting. It must move in a straight line when it uses this action.
  • Spiky. Each time a creature attacks the urchin swarm in melee with an unarmed attack or a natural weapon like a claw or bite, or attempts to grapple or Shove the swarm, takes 1 piercing damage and 2 (1d4) poison damage.
  • Swarm. The swarm can occupy someone else’s space and vice versa. The swarm can fit into any space large enough for a tiny urchin to squeeze through and can use a reaction to attack any creature that leaves its square with an attack of opportunity.
  • Underfoot. Any area containing the swarm is treated as difficult terrain, and creatures swimming or walking through the swarm must make a DC 11 Dexterity saving throw or affected by its Spiky ability.
  • Water Breathing. Ravenous urchins can breathe only underwater; however, they can hold seawater inside their bodies when the tide goes out, allowing them to survive until it returns.


  • Spiny Swarm. Melee Weapon Attack: +3 to hit, range 5 feet, one target. Hit: 3 (1d4+1) piercing damage and 7 (2d6) poison damage, or half as much on a successful DC 13 Constitution saving throw. Creatures failing their saving throw also become poisoned. They can end the poisoned effect with a DC 13 Constitution save each round at the end of their turn, but while poisoned have their speed is reduced by half.

Colorful tentacles writhe across this marine creature like long petals on an immense flower.

Vermin of the Deep. The largest anemones in the ocean are capable predators despite their plodding movement. They lie in fields of other, usually smaller, anemones and among brightly colored coral societies. Deep tiger anemones feed local scavengers by attacking large prey or schools of fish, scattering uneaten remains to their neighbors.

Section 15: Copyright Notice

Sea Monsters (5E) © 2021, Legendary Games; Authors Michael Ritter, Michael “solomani” Mifsud, Robert J. Grady, Mark Hart, Jeff Ibach, Alex Riggs, Scott D. Young, Jeff Lee, Matt Kimmel, and Jason Nelson.

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