The Vex Caves¶

The Vex Caves are real. Long spoken of as a legend of the Harrows — a mage's drowned workshop that no one returns from — they proved on entry to be exactly that: the sealed sea-cave laboratory of a scholar named Theodora, who lived and worked here alone for more than twenty years.

The cave mouth lies about six miles up the coast from Saltmoor, reachable only by boat and only at low tide, when the water inside drops to the ankles. The tide floods back within a few hours — and faster near the end of its rise than the unwary expect — so the window to get in and out is short.

The Gate and the Tide¶

The entrance is a barnacle-crusted iron gate set into the black rock. Framing it are concentric ring carvings in the same survey notation the party first saw in the ruins beneath Aristonia. The gate was once a tide-control mechanism: a great brass flap that could seal the cave against the water. It is now broken and beyond repair without materials no one carries, so nothing holds the tide back any longer.

Inside¶

The caves are a maze of dark, flooded chambers lit only by patches of bioluminescent algae and fungus. The layout is deliberate — a working laboratory with its rooms labeled — and Theodora left carved wayfinding keys and brass plaques throughout, several addressed to "M" and signed "T," to guide whoever might one day come:

The Survey Hall — a domed chamber ringed by a raised stone walkway (part of it collapsed, leaving a ten-foot gap over a rising pool). Its wall carvings point the way onward: the laboratories, the library, the workshop and living quarters far ahead beyond a brass corridor, and the way out through a deep shaft above the workshop. A plaque warns that "the geometry begins to bend further in," and advises orienting oneself here first.
The Lab — a small, near-empty room where Theodora began. On a table sits a clay disc scored with concentric rings, an apprentice-grade instrument that reads the local weave at a glance; a plaque notes that its outer ring, the "brass enhancement," channels the weave more efficiently.
The Library — a sunken chamber of waterlogged shelves, their books pulped to mulch by the sea. Its waters hold swarms of small, sharp-toothed fish that feed on blood and attack in a frenzy once it is drawn. On a plinth at the far end stood a sealed brass-scored iron chest, waterproofed against the sea, holding Theodora's diary and ledger. A side grotto of glowing tide pools — beautiful, but coated in a life-draining moss that must not be touched — held a silver bracelet set with a green stone, engraved "To T, from M, always."
The Brass Corridor — a passage whose walls are lined with thin brass channels that resonate at a low pitch and flare with a sickly violet light. They draw the ambient weave into a single readable line, and passing through produces harmless "dispersion effects": warmth, brief auditory illusions (a woman's voice murmuring "I told you not to come"), shadows that detach and reattach, and spells that come out wrong. A plaque advises walking steadily through and not lingering.
The Tide Chamber — a circular room with a central column bearing three brass arms that swing to plug and unplug the doorways, triggered by floats as the tide rises and falls, marked with a wave glyph. A plaque there notes, with something like pride, that this room is the one piece of the whole work that needs no weave to function — the tide alone drives it — and that in a pinch the float-triggers can be released by hand by climbing to the matching bands on the column. Only one door stands open at a time, so unblocking one seals another.

The Deeper Caves¶

Past the tide chamber the caves open into Theodora's true workspace and, beyond it, the places where the legend of the Vex Caves was earned:

The Workshop, the "Conduit Heart" — the largest chamber, lined with black-stone workbenches and corroded instruments. Raised on a pedestal at its center sits a ring of dark metal etched with concentric channels: the throttle, the heart of Theodora's whole apparatus, to which an attuned instrument reacts more strongly than to anything else in the caves. In one corner stands a sealed brass door with no handle of any kind, its face etched "Conduit heart. Remove the throttle and proceed. Be wary of the tide." — meaning the throttle must be lifted from its cradle to open it, the very act Theodora's diary begs no one to commit. A near-identical smaller room close by holds another such ring: an inert prototype of no special power, but of some worth to a collector. The party ultimately did lift the throttle, and the door ground open — while the tide, as the etching warned, surged in faster.
The Weave-Study Chamber — the room the sealed door had hidden. It is another broad chamber lined with humming brass channels and conduits, all of them converging on a central pedestal, and it connects by a long corridor back around to the tide chamber. This, Theodora's own work made plain, was where she studied the weave: with the throttle seated into its pedestal, the ambient weave became visible as a shimmering geometric lattice of energy filling the room, strong and steady while the throttle held it and gone the moment it was removed.
The Escape Shaft — hidden behind a pressure-stone in the workshop's back wall, a narrow four-foot shaft climbs on good iron rungs to a grass-covered trapdoor that opens onto the clifftop in daylight. This is the "deep shaft above the workshop" the entrance carvings promised — the one way out that does not depend on the tide.
The Specimen Halls — sloping rooms lined with tiered stone shelving and dozens of glass tanks, most long shattered, a few still cloudy with preserved specimens. Deeper in, a chamber holds two great tanks, each containing an enormous centipede-like creature. These were living experiments: their carapaces are dense with metal, and — like the caves themselves — they carry the weave's enhancement worked into living flesh. One broke free and attacked with a paralysing venom before it was destroyed; the other remains sealed in its tank.
The Lair — the deepest, lightless corridor, choked with piles of bones and the corpses of those who came chasing the caves' fabled treasure. This is where Theodora — or the thing she had become — waited in the dark, and where the party finally met and destroyed her.

A Place Where Magic Runs Strong¶

The caves concentrate the weave — the ambient force of magic — to a degree found almost nowhere else, which is why Theodora chose them. Those with magic in them feel their own power strengthen within. But the concentration is unstable: where the brass conduits flare, magic behaves strangely. Theodora's own writings warn, over and over, that the place is dangerous, and that a certain central apparatus — the throttle, seated in its cradle deep within — must never be moved, or the caves will turn deadly.