Midnight brought the spring tide, and with the spring tide came the full weight of the drowned world.
In the deep-sea chambers of the Drowned Dao, tides did not manifest as waves breaking upon a sandy shore. They showed up as an omnidirectional surge of deep water pressure. The twin pale moons lined up with the sub-oceanic rift fifty miles to the east. Then, the water level inside the flooded lower channels rose by forty arm-lengths in less than twenty minutes. The cold, unbending weight of that rising water tightly packed the trapped pockets of hadal air against the ceilings of the entry halls. It drove the air pressure to more than three mega-Pascals.
The first indication of the surge was a change in the pitch of the archway itself.
The forty-arm-length archway of Gate Thirty-One was built of linked arch stones of dressed white green jade, capped at the apex by a three-ton wedge-shaped keystone carved with the ancient seal of the Northern Spirit vein. Under ordinary load, the arch stones rested in static squeezing, transferring the massive upright weight of the mountain above down through the jambs into the living hard speckled rock floor.
At twenty minutes past midnight, the keystone began to cry.
