Siren’s Tail

Medium aberration, chaotic neutral

Armor Class 11
Hit Points 18 (4d8)
Speed 30 ft., swim 30 ft.

12 (+1) 13 (+1) 11 (+0) 2 (-4) 10 (+0) 3 (-4)

Skills Perception +2, Stealth +3
Senses darkvision 30 ft., passive Perception 12
Challenge ¼ (50 XP)


  • Amphibious. The siren’s tail can breathe air and water.
  • Symbiotic Bond. When the siren’s tail is attached to a host, the host gains the following properties. The host can breathe underwater and gains a swim speed equal to twice their walking speed. They retain their normal mode of respiration. They ignore the effects of difficult terrain and standing up from prone costs no movement.


  • Bite. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 4 (1d6 + 1) piercing damage. The target is grappled (escape DC 11). Until this grapple ends, the target is restrained, and the siren’s tail can’t bite another target. If the creature remains grappled in this way for 1 minute, it becomes the siren’s tail’s host.
  • Swallow. The siren’s tail makes one bite attack against a Small or smaller target it is grappling. If the attack hits, the target is swallowed and the grapple ends. The swallowed target is blinded and restrained, it has total cover against attacks and other effects outside the siren’s tail, and it takes 5 (2d4) acid damage at the start of each of the tail’s turns. The tail can have only one target swallowed at a time. If the tail dies, a swallowed creature is no longer restrained by it and can escape from the corpse using 5 feet of movement, exiting prone.


Named for the unique appearance they give their hosts, siren’s tails are water-dwelling aberrations that bind to other creatures by consuming their lower body. Once a host’s lower extremities have been digested, the creature becomes completely reliant on the siren’s tail for survival. Hosts of these aberrations can be mistaken for merfolk from afar, but proximity always reveals the giant leech that consumes its host.

Fluid Dependent. Siren’s tails rely on a constant intake of fluids, whether from a watery environment or a host’s blood supply. To this end, a siren’s tail causes its host to constantly thirst and produce more blood, making sure it always has an ample supply of fluids when out of the water. Though not always immediately noticeable, this process makes a host’s skin semi-translucent and causes it to produce light layers of mucus, which most will simply mistake for excessive sweat.

Muscular Form. Despite its flexibility and grace, a siren’s tail is composed of dense muscle, making it a force to be reckoned with both in and out of the water. In combat, siren’s tails make more use of their body as a weapon than they do of their mouths, which exist mainly for the purpose of binding to hosts. Creatures that find themselves bound to a siren’s tail can learn to make great use of its musculature both for combat and traversing complex terrain.

Alien Influence. The siren’s tail gives its host the following flaw: “I possess a thirst that is never quenched and have a persistent desire to return to the water.”

Section 15: Copyright Notice

Zargoth’s Tome of Familiars, Copyright 2021, Arcana Games, LLC.

Section 15: Copyright Notice

Zargoth’s Tome of Familiars, Copyright 2021, Arcana Games, LLC.

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