If you're thinking of "talisman" as a lucky charm:
* Bad luck charm: This directly opposes the idea of a lucky charm.
* Curse: This emphasizes the opposite of good fortune.
* Unlucky object: This is a more general opposite of a lucky object.
* Omen: This refers to a sign of something bad, the opposite of a positive sign.
If you're thinking of "talisman" as a magical object:
* Ordinary object: This emphasizes the lack of magical properties.
* Non-magical item: This is a more direct opposite.
If you're thinking of "talisman" as something that brings protection:
* Danger: This is the opposite of protection.
* Vulnerability: This emphasizes the lack of protection.
Ultimately, the best antonym depends on the specific meaning of "talisman" in your context.