Prophecy tablet (hatchery)

The Prophecy tablet (hatchery) is an item given to you during Blood Runs Deep, when you have to save King Vargas from Waterbirth Island hatchery. After the quest, it disappears from your possession, even if it is stored in your bank.

The inscription reads, All-consuming Darkness will rise from the sea, unleashed by Good Intent.

This is referring to the Horror from the Deep quest, where after the player killing the first Dagannoth Mother, the stronger version of it is encountered in Blood Runs Deep.