Ferrofluid Ooze

Medium ooze, unaligned

Armor Class 15
Hit Points 52 (8d8+16)
Speed 20 ft., climb 20 ft. (magnetic surfaces only)

18 (+4) 14 (+2) 14 (+2) 1 (-5) 6 (-2) 2 (-4)

Skills Stealth +4
Damage Resistances lightning, bludgeoning from non-magic weapons
Condition Immunities blinded, charmed, deafened, exhaustion, frightened, prone
Senses blindsight 60 ft., passive Perception 8
Challenge 2 (450 XP)


  • Demagnetization. If the ooze takes any fire damage, its Magnetic Field and Magnetic Leap abilities do not function until the end of its next round. Additionally, any grappled or engulfed creature is immediately released.
  • Magnetic Field. Any creature who makes an attack using a ferrous weapon within 30 ft. of the ooze must make a successful DC 17 Strength saving throw or gain disadvantage on the attack.
  • Magnetic Leap (Recharges 5-6). As a move, the ooze can move adjacent to a creature within its magnetic field that is either ferrous or wearing or wielding substantial ferrous equipment (iron armor or a greatsword would qualify, leather or bronze armor, or one dagger would not). This movement does not provoke attacks of opportunity. The ooze then automatically grapples that creature.


  • Pseudopod. Melee Weapon Attack: +6 to hit, 10 ft. reach, one target. Hit: 15 (2d10 + 4) bludgeoning damage.


Ferrofluid oozes can form virtually anywhere, but they are drawn to urban areas filled with magnets and ferrous metals and find solace in any place that thrums with electromagnetism. Their dark, aqueous bodies skulk low to the ground, and they often hide away beside magnetic machines in industrial districts or aboard starships and space stations. A few lucky oozes find caverns of naturally magnetized ore. Wherever the oozes travel, their magnetic properties reduce the vibrations of their movement, making them difficult to detect until their magnetic fields and unmistakable magnetic pull betray their presence. Ferrofluid oozes are usually about 3 feet in diameter.

While not inherently ill meaning, ferrofluid oozes often are at odds with the owners of the magnetic objects they covet. Usually utterly indifferent to organic life, ferrofluid oozes seek only to collect magnetic material— though they do defend themselves, and can attack when stubborn life-forms refuse to relinquish their magnetic goods.

Ferrofluid oozes that collect a large amount of debris are even on occasion mistaken for scavenger slimes.

Magnetic Propagation. As ferrofluid oozes skulk around places profuse with magnetized materials, they occasionally leave behind droplets of magnetic fluid.

So long as these droplets remain in the magnetized environments provided by their parent, their size and magnetic power grow in parallel with their access to additional magnetized material.

Due to this propagation, it is not unusual to see several ferrofluid oozes enjoying the same magnetically charged environment, so experienced adventurers are wary when they find only a single ooze in such a place. Given enough time and magnetic material, multiple oozes can form into a single, much larger ferrofluid magneto-cluster around 8 feet in diameter.

Section 15: Copyright Notice

Mechanical Monsters (5E) © 2023, Legendary Games; Authors: Jason Nelson, Miguel Colon, Robert J. Grady, Nicholas Hite, Matt Kimmel, Michael Mifsud, James-Levi Cooke, Dan Dillon, Mike Myler, Ismael Alvarez, Jeff Lee, John Lynch.

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