The Tiamat Coin is a magical cursed coin used to grant wishes, though a curse cast upon it cause wishes tend to turn out "bad".
The coin originated from Babylonia and bears an image of the serpent goddess Tiamat. Tiamat is the Babylonian goddess of primordial chaos. Using black magic, priests created this coin to sow the seeds of chaos. Since its creation, it has been destroying towns for centuries (according to Dean's research), even wiping some off the map.
This coin was later acquired by Wesley Mondale, who tossed it into a wishing well at Lucky Chin's. This enabled the well to grant people wishes, but with a twist. The wishes will be granted, but not in the way the wisher wanted. For instance, Audrey Elmer wished for a lifelike teddy bear and got one with depression issues.
The coin itself cannot be removed by anyone but the person who first placed it in the well. Once the coin is removed, all wishes are nullified.
- Wesley Mondale wished for Hope Lynn Casey to love him more than anything. RESULT: She would do anything for him, even kill somebody (Sam).
- Audrey Elmer wished for her teddy bear to come alive. RESULT: The teddy bear turned into a "bipolar nutjob."
- A boy wished that he could become invisible so he could go into the women's bathroom. RESULT: He gets hit with the Impala by Dean, who didn't see him due to his invisibility.
- Todd wished to be stronger than everyone. RESULT: Todd goes on a rampage and turns over a car while frightening a group of bullies. Wish reversed.
- Local man wins the lottery. RESULT: Unknown. Wish reversed - the ticket becomes fake.
- Dean wishes for a foot-long Italian with jalapeño. RESULT: He becomes ill from eating the sandwich.
- Audrey's parents wish to be in Bali. RESULT: In Bali. Wish reversed - they get sunburned and deported back.
- Hope wishes Sam dead. RESULT: Sam dies from a lightning strike and Hope becomes much more of a psychopath. Wish reversed - Sam was resurrected.
- Tiamat is the first known deity so far to be related with a cursed magic coin, the second being Binbōgami and his coin.