The Undermarsh were a Nackers' network of muddy tunnels and caves which would, if it were truly part of the natural realm of the Marish, have been drowned in water. It was instead a special part of the Under-deeps, a netherworld of subterranean passages so-called because they underlay the sunlit surface of many lands in Middle-earth. The substance of the Undermarsh parttook of the realm of Shadows. The Nackers, and the more powerful spirits who had once created the Undermarsh, drew strength from Shadow and the dark essences of Arda. The Nackers worshiped these malevolent spirits, taking the magic that held their realm in existence to be a gift from He-Who-Walks-In-Darkness-And-Power, the Vala known as the Defiler, or as the Black Enemy.
Mortals who traveled through the Undermarsh usually sickened and died. The Undermarsh reflected the nature of the powers that created it. These beings considered struggle and pain to be all of existence rather than just one necessary part of it. A predator lurked every few yards in the Undermarsh. Everything that lived here hunted or was hunted; every room and passage could cause pain and suffering. The natural animals that dwelt here were of the sort favored by the Dark Powers (spiders, rats, etc.) or those too witless to be frightened off (fish, worms, and vermin).
Most of the passages in the Undermarsh and some of the chambers were no more than 4' high. Anyone taller than a Hobbit, Nacker, or Muckling had to move in a crouch and fight partially kneeling. Blunt weapons that must be swung could only be used to pummel opponents.
I. Bog-doors. The Nackers and their Muckling henchmen reach the surface world through magical portals. There were a dozen of them functioning in the Marish at the time of their peak. The bog-doors looked, to mortals, to be nothing more than small pools of dark water in the midst of the swamp. Savvy Hobbits and Men avoided stepping in such pools, because a water puddle in the Marish could be harmless or it could be the innocent upper window of a bottomless mud-pot. Children were taught at an early age to avoid wet spots in the marshes. If they stepped in one, they could simply drown, or, as Riverman stories went, they might fall into the nether-world and be eaten by the Nackers, the Mucklings, or the Mudling Annis. A true bog-door was barely large enough to allow passage of an unencumbered Man or the carcass of a deer or sheep. A nonliving object thrusted or dropped into one striked mud a yard or so down. A living creature that entered a bog-door had to swim or climb down through darkness for about 6'; he then broke the surface of a muddy pool in an antechamber of the Undermarsh. The roots and mud that might entangle the creature attempting the passage were not strong, but he had to make a successful maneuver to move through them or else he would drown (eventually) where he sticked. Bog-doors were sometimes protected by brambles . The brambles or other tainted swamp-weeds surrounding the passage could sometimes be detected. If the brambles or weeds were partially or whidely removed, the bog-door became useless for a few days until they grew back. Only if a 10 'x 10' x 10' cube was excavated (difficult in a bog) could the plants be completely destroyed and the door closed forever.
Each portal led into a small chamber, a hollow in the earth roughly 10' in diameter and physically some 40'-80' underground. The air was warm, damp, and breathable, with the smell of soggy garden mulch. The chamber was dimly lit by glowing fungoid growths along the walls. If the Nackers had been making active use of a particular bog-door, litter from their activities would be present, along with some small store of weapons, tools, and gear. Half of these chambers had blind holes alongside the real door. The arrangement served as a sort of trap to drown escaped captives and untrustworthy Mucklings.
2. Root Tunnels. The most common sort in the Undermarsh. Some 4'-5' in diameter, they had rough floors and walls, but were reasonably level otherwise. Water dripped constantly into these passages from above. Roots hung from their ceilings, giving the impression that plants and trees were directly overhead. Worms, beetles and burrowing creatures appeared periodically, reinforcing the illusion. The passages had a sorcerous connection to the swamps of the Marish, providing the Undermarsh with a steady flow of food from the healthier world above. Any attempt to dig upward from the tunnels only reached the surface after the passage of 10-50 feet of earth and, half of the time, 2-20 feet of loose mud and water were encountered. If the tunnel did not collapse immediately, it would "heal" within 24 hours. Most of the time, 100' or so of the root tunnel collapsed on either side of a breach from the surface world.
Only the primary root tunnels are shown on the map. Side branches occured every 60'-100', but only 10% of these led to anything but a dead end.
2. Dry Tunnels. I00'-500' deeper than the root tunnels, these were more typical of the Under-deeps and somewhat more dangerous. The dry tunnels were 5'-25' across, cut through packed earth and Eriadoran limestone. They were dry only by comparison with the rest of the Undermarsh. The air was damp, while springs, pooh, and small streams abound. Under-deep vegetation, (fungi, molds, slimes, and moss) was encountered every few yards, but was seldom dense enough to provide the cold illumination that marked the Nackcrs' favorite caverns. Animal encounters could be almost anything likely to be found in the Under-deeps: bats, long-eared rats, rock-slugs, fist-aphids and other giant insects, walking fronds, hunting lizards, Mucklings, Nackers, and the occasioal cave worm (a burrowing dragon).
3. Dark Pools. Caverns 20'-200' in diameter, with moss-filled ponds at their centers. The pools did not block passage into most side tunnels, because the Nackers maintained paths along their shores. The pools were inhabited by blind fish, legless salamanders, frogs, and varieties of insects and slime. 20% were haunted by corpse-lights or other minor undead. The Mucklings wore a charm against these creatures, and the Nackers just ignored them.
4. Fungal Gardens. Chambers 20'-200' in length and width, I0'-20' high, overgrown with mushrooms and other curious growths, and lit by glowing slime along the ceiling. There was a 10% chance of a finding a Muckling harvest party cutting their way into the foliage. Anyone straying off the Nacker paths or spending more than 2 hours in the garden encountered something dangerous. Most threats were plants that spit spores, acid, or sleep gas'. Unconscious victims were digested by tendrils. Other encounters were with carnivorous insects or centipedes.
5. Tendril Chambers. Like the fungal gardens, but the light was provided by quivering root-like tendrils that grew down from the ceilings. The tendrils snared part of their food from the air , part by growing down to ground level. Certain bats and moths lived among the tendrils, excreting perfumes that repeled their touch; rubbing a dead bat over the upper part of the body was one way to avoid entanglement. The Nackers took the easier course of pruning all tendrils capable of reaching their paths. Tall creatures who walked through a tendril chamber continually risked attack.
6. Spider Chambers. Some 5'-15' across, and crisscrossed by nest webs, the spider chambers were avoided by the Nackers save when they needed silk for clothing and ropes. The Nack-spiders who lived in the chambers were white and cat-sized, the primary small predators in the Undermarsh and, as noted above, a Boglands creature that sometimes accidentally escaped to the surface world. They hunted the many side passages in the root tunnels and accumulated old weapons and other shiny objects in their nests. The Nackers were fond of these spiders and viewed them as pets. If a Nacker used an animal summoning spell in combat, Nackspiders were the creature most likely to appear.
7. Slimes. Smaller chambers overrun with molds, living muds, and similar foul life forms, tolerated by the Nackers because they provided raw materials. Food, tanning steeps, alchemical smears and fluids, poisons, and drugs could be secured here. There was a chance that a surfacedweller would trigger the emission of a poisonous cloud or spray, or touch a smear.
8. Pale Harvest. Like the fungal gardens but tamer.Chance of Mucklings at work, but an escaped captive could hide here.
9. Nacker Nests. Each of these four nests was home to about 20% of the 40 Nackers and 60 Mucklings living in the Undermarsh, The balance dwelled in the Dark Bastion (#10, below), including all the Muckling females and imps. Crude huts were placed in a row around the outside of each 200'-wide nest cavern. Small tunnels led away in all directions, connecting the nests with each other and various rooms in the Dark Bastion. The Nackers did not forge metal and prefered their food unprepared, but they kept quite busy, working hides and fibrous mushrooms, splitting and finishing flint, and abusing the Mucklings and each other. The chamber was lit by torch light brought from the firepillar (also #10, below). Graven runes in a variation of the Cirth and the Melkian tongue were inscribed among the fluorescent molds along the caverns' walls and ceilings. These runes provided magical defense to the nests.
10. Bastion of Dark Worship. A cavern some 150' across and 50' high had been partitioned into smaller chambers set around central hallways connecting to the cave's primary entrances. The hallways met at the center of the Dark Bastion in a 40'- diameter meet-hall; a temple to Morgoth lay just off the meeting hall, separated from it by a wall of magical darkness. The meethall was brightly lit by a yellow flame-pillar reaching from its floor to its ceiling. The pillar was made of stone, but enveloped by weakly flaming gas that enters the cavern through vents at its base. The Nackers lighted torches and lamps from this pillar to work in the smaller chambers nearby; a bit of wood, rag, or any other organic substance touched to this pillar burned cleanly for 6 hours. Any sorcerer standing before the altar in the temple could command the pillar to sweep the meet-hall with a Call Flame spell. The cavern of the Dark Bastion was magically warded and designed so that Nackers could attack invaders with stones and darts from upper chambers. Nacker stonework was not graceful, but effective. The various doorways, arches, and staircases connecting the chambers were designed for their passage; larger beings had to crawl through them.
The temple was a single circular chamber some 40' across, adjacent to the meet-hall, and built from fused black basalt. The wall of darkness between the the temple and the meet-hall appeared and disappeared upon the command of the sorcerers. The interior of the temple, like the nests, was decorated with ancient rune-spells; here, they also covered the ceiling and floor. No furnishings marred the simplicity of the temple chamber, although torture instruments were brought from outside when needed The altar in the middle of the room was a single, 4' x 5' x 3' slab of red-black obsidian written with spells. It was decorated around its base with the skulls of Elves, some of them several thousand years old. A perpetual flame, flickering in colors of deep red, violet, and blue, hovered in the air directly over the altar. Through this flame, the Nackers believed, the Great Defiler spoke to them and might someday give them power to retake all of Middleworld from mortals.
The altar had been enchanted before the coming of the Secondborn to Arda and was indestructible by mortal means.If all the Nacker sorcerers were slain, the altar would sink into the earth for 2-2000 years, destroying the Dark Bastion and the nesting caves with earthquakes, awaiting a summons from some other evil kindred or being. The light was more vulnerable than the altar. If a mortal gazed directly into the fire, he might if sucessful, catch a glimpse of the Necromancer on his throne in Dol Guldur.
- MERP:The Shire