Medium plant, neutral

Armor Class 14
Hit Points 52 (7d8 + 21)
Speed 20 ft.

19 (+4) 10 (+0) 16 (+3) 4 (-3) 10 (+0) 10 (+0)

Saving Throws Con +5
Skills Stealth +4
Damage Resistances slashing and piercing damage from nonmagical attacks
Damage Immunities lightning, fire damage
Condition Immunities prone
Senses darkvision 60 ft., tremorsense 120 ft., passive Perception 10
Languages Common (understands but can’t speak)
Challenge 3 (700 XP)


  • Animate Trees. An algoid can innately cast the animate objects spell at will, requiring no components. Each casting animates two trees, which are all the algoid can control at a time. A newly animated tree takes one full round to uproot itself. Once free, trees act on the algoid’s turn.
  • Vulnerability to Water Magic. Control water and create/destroy water spells deal 3d6 piercing damage to an algoid.
  • Water Camouflage. An algoid has advantage on Dexterity (Stealth) checks when it has any type of standing water to blend into.


  • Multiattack. The algoid makes two Slam attacks.
  • Slam. Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 8 (1d8 + 4) bludgeoning damage. If an algoid scores a critical hit with this attack, the target must make a successful DC 14 Con saving throw or be stunned. The stunned creature can repeat the saving throw at the end of each of its turns; the condition ends on a successful save.
  • Mind Blast. Each creature in a 60-foot cone must make a successful DC 13 Intelligence saving throw or be stunned for 3d4 rounds.


Algoids often resemble green humanoids, though they can just as easily take the appearance of a mound of green sludge or even spread out to blend into a scum-covered pool. The creature is not one being; it is an intelligent colony of algae awakened through some means. Usually this is through a magical accident, though some scholars believe an overuse of magic in fragile natural settings can cause an algoid to form. Others say the algoid is a natural magical expression tied to marshes and swamps, and the ability of the algoid to “awaken” trees to join in the defense of its home lends some credence to this theory.

The “skin” of an algoid is coarse and rough with a leafy texture. In its natural surroundings, it is nearly invisible until it attacks. Algoids use this natural camouflage when prey is nearby. The algoid lies in wait, submerged in water or a bog, as it watches its prey. When a potential victim passes nearby, the algoid springs to attack. It is roughly humanoid in shape and resembles a green humanoid. Algoids make their lairs in marshes and swamps. They are often encountered with other marsh-dwelling sentient plants; though never with shambling mounds (they hate them and usually attack them on sight).

The algoid is 7 feet tall and weighs about 300 pounds. In its natural surroundings, it is nearly invisible until it attacks and uses this to its advantage when prey is nearby. The “skin” of an algoid is coarse and rough with a leafy texture. The algoid often lies in wait, partially submerged in water or a bog, until its prey passes nearby. It springs to attack with its powerful fists when its opponents come within range.

Section 15: Copyright Notice

City of Brass ©2018 Frog God Games; Authors: Casey Christofferson and Scott Greene

Tome of Horrors 2020, (C) 2020, Necromancer Games

This is not the complete section 15 entry - see the full license for this page