The talismans were a set of four magical keystones designed by the keepers to unlock the Elemental Wards placed on The Haunted Cathedral. The talismans were the only known items capable of opening the wards. After the Keepers sealed the cathedral, they scattered the talismans across The City in two (or in Thief Gold, four) different places.
The Talisman of Earth was originally hidden in one of the heavily-guarded towers of the mages of the Hand Brotherhood. The strength of the mages' magic and the confusing and complicated design of the mage towers made this talisman extremely difficult for Garrett to recover.
The Talisman of Fire was concealed at the top of an old tower deep within the Lost City of Karath-din. The state of the city's deterioration and lava flows of the caverns combined with the fact that almost no one in the City even knew of the existence of the Lost City made this an ideal hiding spot for a talisman.
The Talisman of Water was hidden in a cavern under the old quarter of the city. The cavern had been rigged by the Keepers with multiple tricks and traps. Unfortunately, this was the least effective of the four hiding places, and the talisman of water was eventually discovered by workers of Lady Valerius, owner of the Opera House, where it was subsequently placed.
The Talisman of Air was given by the Keepers to the Hammerites to guard. They kept it locked and guarded deep within the City's Hammer Temple. Garrett entered the temple by pretending to be a Hammer novice and was eventually able to recover the talisman.