Monster Analysis: Gelatinous Cube

Thanks to @AcidburnKG for this art piece!

  • Encounter Appearance: 2-15 Where the River Goes
  • Armor Class 6
  • Speed 15 ft
  • Blindsight 60 ft, Passive 8
  • Immune to blinded, charmed, deafened, exhaustion, frightened, and prone
  • Suggested average, max HP: 84, 120
    • 152 taken, 22 HDYWTDT by Yasha

Oozes, as Liam put it, are classic Dungeons & Dragons foes. Rumored to be the fragments of a demon lord, these unaligned beings have nearly no intelligence (most carry a -5 modifier) and no dexterity (the cube is the slowest of oozes with a -4 modifier), but a hunger that eternally seeks out organic beings to devour. Most oozes don’t have enough sentience to have any sense of drive beyond eating whatever is near it, so they can be very easily controlled by someone who wants to use an ooze as part of a trap. (Way, way back in the early days of Critical Role, Vox Machina faced its first and only ooze, a black pudding.)

The gelatinous cube that The Mighty Nein encountered was set as a trap for whoever tried to get into Siff’s laboratory. Each type of ooze dissolves different materials. Gelatinous Cubes’ acid consumes living tissue, but not bones, metals, or stone. Judging by how empty the cube was when it fell from its ceiling container, it had either been up there, alone, for a very long time, or conjured with an empty stomach to punish those who attempted to enter the wrong combination.

A gelatinous cube is nearly the complete opposite of the will-o’-wisps the Mighty Nein faced earlier. Whereas the wisps were swift and had very little health individually, the cube was a slow-moving, easy-to-hit sack of hit points. Given a chance to move, the cube can attempt to Engulf nearby snacks of large or smaller size by moving into the space they occupy. Creatures the cube attempts to engulf can attempt a dexterity save to sidestep it, but failing to move sucks them inside for an initial 3d6 acid damage (and allows the DM to use the cube’s miniature as box by placing the players’ minis inside of it). Until they attempt a strength save to escape or a friend attempts to pull them out, they take a continuing 6d6 at the start of their turns. (To put that damage in perspective, 3*6 + 6*6 = 54 full acid damage would be enough to kill any member of the Mighty Nein.)

Unfortunately for Matt but fortunately for the Nein, Caleb’s Earthen Grasp prevented the cube from moving, and therefore from swallowing any party members (Frumpkin included). It still managed to use its acidic psuedopod to strike at Yasha and Jester, including a critical on the latter that downed her in a single attack. However, by the time the cube broke free of the Earthen Grasp, the Mighty Nein had already managed to deal 117 damage to it. With Beau leading with 44 total damage, Yasha with 43 damage, and Nott with 39 damage to the cube, Yasha finished the cube so the party could refocus their attention on the laboratory’s puzzle.