A knell beetle was a monstrous breed of insect that formed warrens underground and wielded great sonic powers. The lesser knell beetle was the worker drone of the species.
It was a huge beetle-like insect with a shiny red and black hard carapace; this appeared as though it concealed wings, but it had none. It had twelve limbs in total: ten legs descending from the thorax and two arms from the sides, which were jointed and dexterous and ended in piercingly sharp hooked claws. The head part was small, holding four sharp and jagged mandibles, two small and two very long, and four beady black eyes below a chitin brow ridge.
The most obvious feature of the knell beetle was its chitin horn—a massive bell- or trumpet-like structure that jutted forward from the top of the head, tapered over the shoulders and flaring widely out in front of the head. This horn emitted high-pitched warbling and trumpeting, faint when dormant, louder when communicating or attacking.
A regular knell beetle grew up to around 9 feet (2.7 meters) long and weighed around 1500 pounds (680 kilograms). A lesser knell beetle was 4–5 feet (1.2–1.5 meters) and weighed 180–200 pounds (81–91 kilograms), being about the size of a pony.
As insects, knell beetles were mindless creatures, acting pure on instinct.
The black chitinous exoskeleton and thick red carapace provided the knell beetle with a very strong and durable armor. The knell beetle was possessed of darkvision and scent, the ability to burrow through the ground, and great skills in balance, hearing, and sight.
From its trumpet, once a day, a knell beetle could emit a devastating cone of sound. This sonic energy harmed all creatures caught in front who could not evade it. The regular knell beetle made an intense chiming sound, potent up to 30 feet (9.1 meters), while the lesser knell beetle made a weaker screech, up to 20 feet (6.1 meters).
The knell beetle was entirely immune to sonic energy, and in fact was healed by it. Sonic energy could restore a knell beetle back to full health, but could not bolster it further. Despite being weaker in most respects, the lesser knell beetle was more efficiently healed by sonic energy than the regular knell beetle. Knell beetles could thus use their chimes and screeches to heal one another. They would not resist other sonic spells and effects, however. 
Perhaps the knell beetle's most destructive ability was its power to shake the very earth. By making a rhythmic stomping action, they channeled their internal sonic energy into the ground, causing the area around them to lurch and shudder. Beings standing in range risked being thrown to the ground. One knell beetle alone caused shaking effective up to 5 feet (1.5 meters), but multiple knell beetles stomping at once induced a resonance effect: two knell beetles 5 feet apart caused shaking effective up to 10 feet (3 meters), three knell beetles together were effective up 15 feet (4.6 meters), and so on. Knell beetles themselves were immune to this, of course, and could do it as often as they liked.
Knell beetles attacked with their vicious claws and mandibles. Worse, they could latch onto prey with both claws and rend their flesh. They could also knock over and trample a victim. Despite being simple insects, knell beetles fought with some brutal cunning, thought to be a remnant of their creation. And thanks to their unique abilities, knell beetles deployed with some highly organized tactics.
Alone or in group of one kind of knell beetle, they shook the ground to knock over their opponents, then charged and trampled them, finally finishing them off with the bites and claws. They held their sonic blasts in reserve, preferring to heal each other.
In mixed groups, regular and lesser knell beetles instinctively adopted a distinct tactic. The lessers formed a defensive line in front of the regulars, who could then encompass more knell beetles within range of their sonic chimes. The lesser knell beetles were more efficiently healed, and could fight longer than they otherwise could. Thus they often appeared more resilient to other beings.
Knell beetles of either kind were typically found as lone hunters or in colonies of three to twelve regulars, or in colonies of twelve to twenty-four lessers with three to twelve regulars. When a colony grew too large to be supported by an area, usually at fifty members or more, some broke off to form a new colony elsewhere.
Regular knell beetles focused on hunting for prey, breeding, and extending their underground warrens or founding new colonies. Lesser knell beetles, meanwhile, were the equivalent of a beehive's worker drones. They scavenged for good, built and expanded nests, and fought in the frontlines to protect the colony.
Knell beetles dwelled underground, digging extensive and highly convoluted networks of tunnels. These faintly resembled those found inside anthills.
Some Underdark races employed knell beetles as mounts. Some hobgoblin and orc communities even domesticated them from time to time, making use of their greater power in numbers. Squadrons of knell beetle riders were even occasionally the elite corps of the armies of some tribes and cities.
In the Year of Lightning Storms, 1374 DR, the Shadowscale lizardfolk kept a lesser knell beetle in a cage in their mound-fort in the Shadow Swamp in the Plane of Shadow. They released it to attack intruders into their warren.
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 Andrew Finch, Gwendolyn Kestrel, Chris Perkins (September 2004). Monster Manual III. (Wizards of the Coast), pp. 88–89. ISBN 0-7869-3430-1.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Richard Baker, Bruce R. Cordell, David Noonan, Matthew Sernett, James Wyatt (2007). Cormyr: The Tearing of the Weave. (Wizards of the Coast), pp. 82,102–103. ISBN 07-8694-119-7.