The Hydro-lunarium isn't a place, not precisely. It’s a state. A confluence. A harmonic distortion woven from the tidal rhythms of forgotten oceans and the fractured echoes of lunar contemplation. It began, according to the fragmented logs recovered from the Chronarium of Aethel, with a singular, intensely bright bioluminescent bloom – a species of jellyfish now referred to as *Lumina Maris Profundi* – that occurred during a conjunction of Jupiter and Saturn, coinciding with a rare meteor shower composed entirely of solidified temporal particles. These particles, it's theorized, acted as conduits, amplifying the jellyfish's natural resonance, bending the fabric of spacetime around it.
The Chronarium of Aethel, a marvel of temporal engineering, was designed to observe and, theoretically, record the consequences of such events. However, the Chronarium’s final entry, a chaotic cascade of glyphs and distorted soundwaves, suggests the *Lumina Maris Profundi* didn't merely observe time; it *became* it. The bloom solidified, creating a localized pocket – the Hydro-lunarium – where the laws of causality shifted like currents in a subterranean river.