Shinsoo (신수 (神水),
shinsu, literally "divine water") is a substance that flows through and is produced by
the Tower. Each
Floor has areas of varying amounts of Shinsoo density, increasing with each Floor. In lower concentrations, its density makes the substance act like a gas, but in higher concentrations, it behaves like a liquid.
Shinsoo's most significant difference to air is the laws by which it operates. Unlike air, which uniformly conforms to the laws of pressure when flowing, shinsoo has no unifying laws. It flows entirely differently in different places and Floors, at both it's own whim and that of the Guardian of the floor. The flow of shinsoo determines its qualities, allowing it to appear as water, fire, light and other phenomena and materials. Shinsoo has no singular property or feature, and is rather the very basis of all energy and things within the Tower.
Shinsoo is essential for living in the Tower, as it allows for breathing and provides moisture for the inhabitants.
Lero-Ro stated that within the Tower, Shinsoo replaces air and carries out all the processes that air would.