The Leng Spiders are not the Night-Gaunts' prey. They are the night-gaunts' problem. That sentence inverts every assumption a casual reader brings to the file, and that is the correct effect. The night-gaunts are the iconic carriers of the Dreamlands cold waste, terrifying to dreamers and apparently invincible against ordinary opposition. The Leng Spiders are what makes the night-gaunts nervous.

This is not a species that has been studied in the conventional sense. It is a species that has been survived, and the survivors have filed reports, and the reports are consistent enough to constitute a file.

The Form

Massive arachnids. Body the size of a draft horse. Leg-span up to twenty feet at full extension, though field sightings rarely catch the specimens at full extension because full extension is what happens immediately before the strike. Dark chitin polished to something between obsidian and wet iron. Multiple eyes arranged in patterns that suggest the visual system is doing something more sophisticated than simple light detection — the geometry of the eye cluster does not match any known terrestrial arachnid and does not match anything in the comparative anatomy Pnakotic fragments either.

Distinct from Atlach-Nacha in that they are a population species, not a unique individual. The population is large enough that the Bureau's working estimate runs into the thousands. Atlach-Nacha weaves the bridge between worlds. The Leng Spiders weave the webs between the rocks, and there are more rocks than there is bridge.

Habitat

The The Plateau of Leng is their home territory. The plateau's overlap between the Dreamlands and waking Asia means the spiders can be encountered in both, though the Asian sightings are rare and uniformly fatal to the human witnesses. Within the Dreamlands, they extend across the cold waste north of Inquanok, with concentrations near the yellow monastery and the high passes of the Plateau of Leng proper.

The density map the Bureau maintains is a density map of rumor. No expedition has surveyed the plateau at a resolution fine enough to produce a real count. The expeditions that have tried did not return with usable data. One returned with a single surviving cartographer and a partial map annotated in a hand that was not his own.

Webs

The Leng Spiders construct webs that operate as both physical traps and — according to the Pnakotic Manuscripts, corroborated by three independent field observations — something closer to communication arrays. The web strands carry vibrations across distances longer than the strands' apparent length, which is the kind of detail that suggests dimensional engineering rather than simple silk-on-air mechanics. A spider in one part of the plateau can detect a disturbance in a web on the other side of the plateau within seconds. The Bureau's working physicist has looked at the math and declined to publish.

The webs themselves are nearly invisible against the plateau's grey rock. Expeditions learn to spot them by the small bones caught in the lower strands.

Intelligence

Tactical coordination has been observed. Spiders working together to ambush large prey. Spiders directing other spiders to flank approaches. Spiders responding to threats with patterns that imply learning across encounters, not just within them. The 1931 Ashcroft expedition recorded an incident in which a pair of spiders deliberately herded an investigator toward a third, concealed specimen — a three-body ambush that required planning, role assignment, and the patience to hold position.

The Bureau's working estimate places their cognitive capacity in the range of advanced primates, with the qualifier that the cognition is shaped by a sensory environment so different from the human one that the comparison breaks down past the basic capacity assessment. They are smart. What they are smart at is not something the file can usefully describe.

The Night-Gaunt Conflict

Documented in the Pnakotic Manuscripts and corroborated by the surviving fragments of the Carter expedition records. Night-gaunts and Leng Spiders maintain a stable territorial standoff in the cold waste. Neither population has been able to displace the other, but the boundary is patrolled, contested, and occasionally violated, and when violations occur the casualties are heavy on both sides.

Randolph Carter witnessed one of the engagements during his Kadath expedition and described it as the only event in the Dreamlands that made him doubt the night-gaunts' reputation for invincibility. His notes describe a night-gaunt pulled from the air by a web strand that should not have been where it was, and the aftermath, which he chose not to transcribe in full. The fragment that exists ends mid-sentence.