Source: Volo’s Guide to Monsters p. 191, Mythic Odysseys of Theros
The quest for revenge sometimes leads one to undergo a ritual whereby they transform into a body of semiliquid sentience known as a slithering tracker. Innocuous and insidious at the same time, a tracker flows into places where a normal creature can’t go and brings its own brand of watery death down upon its quarry.
Vengeance at Any Cost
The ritual for creating a slithering tracker is known to hags, liches, and priests who worship gods of vengeance. It can only be performed on a willing creature that hungers for revenge. The ritual sucks all the moisture from the person’s body, killing it. Yet the mind lives on in the puddle of liquid that issues forth from the remains, and so too does the subject’s insatiable need for retribution.
Stealthy Assassins
A slithering tracker tastes the ground it courses over, seeking any trace of its prey. To kill, a slithering tracker rises up and enshrouds a creature, attempting to drown the prey while also draining it of blood. A slithering tracker that has killed in this fashion becomes much easier to locate for a time, since its liquid form becomes tinged with blood and its body leaves a visible trail of the stuff behind it.
Descent into Madness
Achieving revenge against its target doesn’t end a slithering tracker’s existence, nor its hunger for blood. Some slithering trackers remain aware of their purpose and extend their quest for vengeance to others, such as anyone who supported or befriended the original target. Most of the time, though, a tracker’s mind can’t cope with being trapped in liquid form, unable to communicate, and driven by the desire for blood: after a tracker fulfills its duty, insanity takes over the creature, and it attacks indiscriminately until it is destroyed.
