While at first glance they resembled a pool of water or, if active, a small water elemental, their "bodies" actually comprised a weak acid. As they killed more creatures they would accumulate more and more indigestible metal items such as coins, buckles, or other effects, but they were otherwise completely invisible in water. On land, they moved laboriously, similar to a slug, and were unable to climb hills owing to their semiliquid bodies.
Aballin had no eyes, and tracked prey through scent and vibration.
These animated liquids would entrap and drown any creatures they caught within their reach. They would passively lay in wait in standing water, such as natural pools, subterranean lakes, and even fountains and attack when they sensed prey nearby. When they were ready to strike, the amorphous ooze would change their shape to a 10' (3 m) column of liquid and attempt to drown their target with pseudopodic appendages.
Edged weapons were ineffiective against aballins. When they were active, aballins were immune to elemental effects such as fire, cold, or electricity. In their passive state they had the same properties as water, and were susceptible to water-affecting spells.
While aballin could be found on dry land immitating puddles, ditches, or even fountains, they were most often found in places with plenty of water into which they could disappear. They scavenged and hunted in and around rivers and lakes (both above and below ground), and were known to keep down populations of harmful creatures and plants in these environments. The weak acid compising their bodies could dissolve organic material over the course of two tendays. Inorganic material which remained in their bodies—sometimes including coins or jewelry—could be used as bait to lure intelligent prey.
While often encountered alone, they would sometimes travel in family units of up to four. A mated pair of aballins could merge together to defend themselves or their offspring, effectively creating a double-sized aballin.
In Northwest Faerûn, some were known to dwell within the Mere of Dead Men. They were more often found in Faerûn near the waters in and around the Anauroch desert, specifically the rivers originating in the Desertsmouth Mountains including the Tesh and Ashaba flowing east and the Sixstreams River flowing west. In the Unapproachable East, aballins could be found in Lake Ashane and in the Umber Marshes.
The first aballin was created during the days of ancient Netheril when a druid was cursed by a powerful archmage near her home by the Hale River. It was believed that all the aballin on Toril were descended from this long-dead druid, and the first of them spread out from the Hale River and other waterways of eastern Netheril.
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