The cornucopia is an important symbol of . but in which fantasy series is it a dispenser of weapons and supplies?

The Hunger Games.

In the book series The Hunger Games, the Cornucopia is a giant golden horn-shaped cone with a curved tail, much like the Thanksgiving cornucopias. Every year, the the tributes start off in a semicircle, equidistant to the Cornucopia. This is filled with supplies and weapons that will help the tribunes.