The Wailing Coin drops from Odalrik the Maw.
As a quest objective
This item starts 
[60] Wailing Coin.
Criteria of
Trivia
- The flavor text was changed during the beta from "A strange coin from a forgotten time, somehow imbued with cries of the suffering. Ve'nari will be interested in this." to "An odd coin from a forgotten time, hauntingly imbued with the cries of suffering souls. Ve'nari may recognize its value." The text was changed slightly and moved to the description of the quest.
Patch changes
Patch 9.0.2 (2020-11-17): Added.