Old Tom's Well

"'Careful, Captain,' a signaller whispers. 'Lest the well-winds take us.'

"Below, beneath the scudding clouds, a speckle of structures cling to a shelf of ice. The well-winds drag at your engine like the frantic clutch of a drowning man. The well gapes."

Old Tom's Well is an anomaly in the Reach. This black hole, surrounded by ledges of black ice, is one of the many space-wells of the High Wilderness. It is named after the prospector who discovered Lustrum after making a wish to the well.

Several beehive huts have been built into a cliff of nearby black ice; the inhabitants are mostly prospectors, desperate to repeat Old Tom's luck and strike it rich. There is also an enclave of the Compassed, or Psalmists.

Old Tom?

"Old Tom was a prospector during the Promised Days that followed London's arrival in the heavens. For years he combed the Reach, looking for the strike that would make him rich. He didn't find it. Luckless and impoverished, he made a wish here, at the well. The next month, he discovered the Mother of Mountains and the rich hour-veins that riddled her flanks. For a year – before his disappearance – he was staggeringly wealthy. Others come here now – the desperate and the broken – with their final, futile wishes."

Psalmists

"The ignorant call us the Cursing Church. But we are the Compassed, who dwell on the brinks. We are the lambs who were torn by the wolf. We are the undone. And the angel of the pit hears us, where it would not hear others."

The Psalmist is a brand new religion of the heavens. Led by the Lank Minister, they follow their only sacred text: Psalm 109. They'll accept anybody willing to confess their sins - and blame someone for them.

What's inside the well? [Spoilers for Ambition: The Truth]

"They rage against the sun's death at the hands of a half-sun, a midnight murderer. The killer sent false messengers bearing a well-seed. They planted the seed in the sun's heart, and it bloomed! Bloomed and ravened. A lawless killing! A shameful death, enacted without due ceremony!" Deep inside the well is the corpse of the missing Garden-King, regent of the Reach. The Halved sent a false-messenger bearing a Correspondence sigil of peace and truce. The regent did not know that this sigil was fake, and the false-messenger secretly carried a "well-seed," which bloomed inside the star's heart, killing it instantly. The false-messenger, not knowing its master's scheme, felt guilty for its act. This caused cancerous polyps riddled with sigils of guilt to grow in its heart, killing it as it made its way to Eleutheria.