The choked cistern · Velstraven

A major room of chapter 5. When you walk in, the room card reads: A student is trapped behind the cistern trellis, cut off from the entrance.

Narrated walkthrough

The choked cistern from its entrance — The choked cistern: how to solve it

Getting there

Chapter 5, on the lowest floor, off the Deep protection complex hall through the arch signed The choked cistern. The thermal latch vestibule and the drip-ladder passage open off it. Reach chapter 5 from the drowned hall (chapter 4): once its framework is cleared, the passage beyond leads to a winding stair down to the Deep protection complex.

What is wrong

Room card: "A student is trapped behind the cistern trellis, cut off from the entrance." A heavy hinged trellis has fallen across the refuge on the island. Two fire blossoms burn by the walls, and each has a sensor piped to a flood inlet above the basin. The moment you step into the room, the inlet starts pouring in water.

What you can work

Blossom 0: The left fire blossom; its sensor feeds the flood inlet while it burns.
Blossom 1: The right fire blossom, with the same kind of sensor.
Span 0: The ledge gap: open water between the entrance ledge and the stone pillar, with stone seats on both sides.
Span 1: The island gap: open water between the stone pillar and the island.
Trellis: The fallen hinged trellis. Loaded as it is, it binds at its hinge.
Trellis catch: A service catch above the refuge that holds the trellis once it is turned up to it.
Student: The trapped student, who follows you only as far as the next safe supported landing.
Drain vine: A thin vine wound through the outflow handwheel's spokes.
Drain: The handwheel of the closed outflow gate that drains the cistern into a receiver below.
Reading lamp: Optional light to read by.
Reading shutter: Optional second light angle.

Solution

A nudge

Flooding starts the moment you enter. Binding outside the room means no seconds lost.

The full solution

Before stepping in, bind Supply liquid (Water, Water, Water), Span (Wind, Growth, Growth), Suspend (Will, Will, Will) and Orient (Water, Will, Will) to your four slots.
Flooding starts the moment you enter. Binding outside the room means no seconds lost.
What you see: "Bound to slot N." for each.
As soon as you are in, cast Supply liquid at Blossom 0 and at Blossom 1.
While either blossom burns, its sensor drives the inlet at 400 litres a second. Two wet, dark blossoms stop the inflow, and nothing in the room relights them unless you Heat them.
What you see: "Water quenches the blossom seen by the protective inlet sensor." When both are dark the card shows: both fire blossoms are dark.
From the entrance ledge, cast Span at Span 0 (the ledge gap) and at Span 1 (the island gap).
Each gap has solid stone seats on both sides. A woven bridge seated on them is a walkway for you and the student.
What you see: "The woven bridge seats on two load-bearing stone supports." The card adds: woven spans reach the island.
Cast Suspend at the Trellis.
The trellis's own weight jams its hinge. Holding the weight frees the hinge to turn.
What you see: "The hinged trellis's weight is held."
Cast Orient at the Trellis four times.
Each turn swings it a quarter of its hinge sweep. Four turns lift it clear of the refuge; three are not quite enough.
What you see: "The trellis turns through its clear hinge sweep." each time; then the card shows: the fallen trellis is turned up off the refuge.
Walk across both spans to the island and Handle the Trellis catch.
The catch holds the raised trellis by itself, so it stays up if the Suspend is ever dismissed.
What you see: "The service catch holds the trellis clear of the refuge."
Handle the Student, then wait while they walk out over the spans (about 15 seconds).
The student moves only along a safe supported path. Over the two spans that path leads all the way to the entrance.
What you see: "The student follows only as far as the next safe supported landing." Then "The choked cistern settled."

Other ways that work

Lighten (Wind, Wind, Will) cast at the Trellis instead of Suspend also unloads the hinge: "Upward assistance unloads the trellis lever."
Once the trellis is unloaded, Handle the Trellis to turn it (four presses, from the island) instead of casting Orient.
Drain the cistern instead of bridging it. Sever (Fire, Fire, Fire) at the Drain vine ("The thin fouling vine parts beside the outflow handwheel."), then Handle the Drain ("The outflow opens into its visible lower receiver."). The outflow takes 1,200 litres a second, faster than the inlet's 400, so it also stops any flood. Below 5,000 litres the bed is dry, and you and the student use the service stairs across the floor instead of spans.
If only the island gap is bridged, the student walks as far as the stone pillar and waits there until the ledge gap is bridged too.

Watch for

Timing: from entry the inflow takes about 100 seconds to fill the cistern. After about 75 seconds the warning "Rising water is reaching the refuge." appears.
The flood keeps rising after you leave. If you walk through to the thermal latch vestibule or the drip-ladder passage with a blossom still burning, the cistern fills while you are away and counts as failed when you come back. Quench both blossoms every time you pass through.
Heat on a quenched blossom dries it. One Heat leaves it damp and dark; a second dries it fully and it relights.
Dismissing the Suspend (middle click / Circle) before the catch is set lets the trellis sink back down.
You cannot dismiss a span while the student is on it: "The student is still on this span; let them reach its stone landing before releasing it."
Chill, Obscuring veil and Sever do not put a blossom out; the flame keeps burning or the sensor still feels it.

If it goes wrong

If the water reaches the refuge, the room fails: "Rising water reached the refuge. You and the student are safely back at this room's entry state. Earlier progress is retained." The pause menu opens and the cistern goes back to how it was when you first entered: blossoms lit, no spans, trellis down. Other rooms are untouched. A student already rescued stays safe on every later retry.

Achievements here

No One Left Behind: Solve the choked cistern.
Dry Feet: Dry Feet: never let this room fail on this journey. Bind before entering and quench Blossom 0 and Blossom 1 first. After that the water never rises again, so the rest needs no hurry. Danger points: passing through on your way to the side rooms with a blossom still lit (the room then fails while you are away), and Heat landing twice on one blossom. A failure is recorded at once and survives a restart from the autosave. Only loading a manual save made before it removes it.
Held and Turned: Held and Turned: the standard route earns it here. Suspend the Trellis, then Orient it within 20 seconds.
Light as a Feather: Light as a Feather: cast Lighten at the Trellis, then Suspend at the Trellis within 20 seconds. The trellis accepts both.
A Warm Bath: A Warm Bath: cast Supply liquid at a blossom, then Heat at the same blossom within 20 seconds. One Heat leaves it damp and dark. Do not Heat it a second time, or it relights and the flood resumes.
Four Spells, One Room: Four Spells, One Room: the standard route accepts Supply liquid, Span, Suspend and Orient in this room, so finishing the rescue earns it. A failure wipes the room's list, so it has to happen on the attempt that succeeds.
Flurry: Flurry: with all four spells bound, quench a blossom, bridge a gap, Suspend the Trellis and Orient it within ten seconds.
A Wing Before Lunch: A Wing Before Lunch: this is chapter 5's longest room. Allow two to three minutes for it in a 20-minute chapter run.

Spells used

Supply liquid, Span, Suspend, Orient, Lighten, Sever.