Environment underground
Organization solitary or nest (2–5)
Treasure none

Helix moths are solitary creatures, though on rare occasions a mated pair might be encountered. The lair of an adult helix moth is almost always above ground and usually takes the form of a cave, tunnel, or other such structure. Such places are always well-hidden and difficult to reach. When the time comes for a female helix moth to lay her eggs, she hollows out a tunnel in the floor of her lair, forms a large chamber at the end of the tunnel and deposits her eggs in the chamber.

Helix moth larvae lair in a large, 6-foot-diameter ridged tunnels that burrow down into the earth where they eventually open into a large chamber at least 20 square feet in size. A thick, gray-white slime coats the chamber’s floor and walls. Though harmless to living creatures, but generally not pleasant to touch or come in contact with. Occasionally (15% chance) the secretions of the helix moth larva mix with the slime just enough to form a deadly inhalant poison that affects living creatures within the chamber. Those breathing the fumes must make a successful DC 15 Fortitude save or suffer 1d4 points of Constitution damage. A new save must be made every minute. Once a successful save is made, that creature cannot be affected by the fumes again for one day.

To lay her eggs, the female helix moth uses her acidic secretions and sharpened mandibles to tunnel a hole into the ground and hollow out a large chamber where she lays 2d4 eggs of greenish-gray color. The eggs hatch two weeks after fertilization, producing the helix moth larvae, though typically only about 50% of the larva live past the first day.

Helix moths are normally passive creatures except when hunting. During a search for prey, the creature becomes highly aggressive and does not hesitate to attack any creature it encounters. A helix moth often journeys up to a mile or more away from its lair in search of prey. Slain prey is carried back to its lair and devoured over a period of several days. The adult helix moth attacks by biting or stinging its prey. Its constant droning affects those that combat it, so the helix moth always tries to stay airborne and within range where it can use this ability while staying out of melee range. Helix moth larvae attack by biting.