Tome of Conjure Water

Source
This tome drops from elites in most high-level Burning Crusade dungeons, such as Tempest Keep, Shattered Halls, parts of Auchindoun, The Steamvault, Caverns of Time, Karazhan and also in heroic dungeons.

This tome, along with the Tome of Conjure Food VIII, was necessary to learn Ritual of Refreshment from Mage trainers. Right now it's useless.