The crystal trident of the so-called "River God" Poseidon was found at the bottom of the Lake of Tears, and taken into possession by the man that would soon after become the Second Dungeon Master in 948 GUE. He placed it into the trophy case and it was last known to be for sale by Ellron in the same year.

Some have attempted to placate Poseidon by downloading their inventory into rivers. Due to unsuccessful answers from this pseudo-god, many have been lead to believe that he does not exist, however a popular legend tells that after Odysseus blinded a cyclops (who happened to be Poseidon's son Polyphemus) and teased him, that the cyclops called out to Poseidon to curse Odysseus. Enraged Poseidon, barraged Odysseus' escaping ship with tremendous storms.

SOURCE(S): Zork I, Dungeon