Day of the Sepulchral Night

The Day of the Sepulchral Night was a solar eclipse on Zelos II that occured around every 120 years. When's the planet's fourth moon was in line with the sun, the tides in the Great Zelosi Sea were at their lowest, which in turn gave access to Zelosian's Chine: a underwater mountain ridge said to contain a legendary treasure buried by a merchant prince.

The native Zelosians, superstitious of the event, stayed indoors for its duration.