Pebble of Truth

Esp hstdapcd. . . Espj'cp pgpcjhspcp. . . Zywj I dstqe ty etxp xlj cpgplw hspy esp ecfp xplytyr htww dszh. . .
The Pebble of Truth is an item purchasable from The Oak Depot for $55,000.
==Details==
The Pebble of Truth is an intentionally cryptic item. The description is ciphertext, and the Pebble emits a quiet whispering sound.
For those who wish to try to solve the mystery themselves, the rest of the details will be hidden in a spoiler section:
 
:⚠ WARNING! This section contains spoilers. Read at your own discretion.
The description of the Pebble of Truth is encrypted using a Caesar cipher, rotated 11 positions to the right. The actual description is as follows:
The whispers. . . They're everywhere. . . Only X shift in time may reveal when the true meaning will show. . .
While the description nor the whispers provide any hints as to where to take the Pebble of Truth, it must be taken to the Duck Shrine beneath the short arch bridge in Finlay. The Duck Shrine emits the same whispers as the Pebble of Truth does. Placing the Pebble there causes the shrine to begin charging up before letting out a massive explosion of energy, turning the Shrine's light red. The Pebble of Truth will not be consumed. The altar cannot be activated again by any other Pebble of Truth, but the same Pebble of Truth can be used to activate shrines in servers where it has not been activated.