The Jaguar Pendant was an artifact hidden near Lucasio, Mexico. Indiana Jones recovered the pendant in the course of his adventures in Mexico in the 1930s.
The Nazis tried to find the Pendant for unspecified reasons. They kidnapped Marcus Brody and offered Indiana Jones the opportunity to save his colleague by finding the artifact for them.
Jones eventually found the Pendant but noticed that it was fake. He gave it to General Anton Schlossberg, who believed it to be genuine, and thus released Brody.