The Golden Fever is the event where you have the chance to get golden and overall more valuable gems during the attacks. 

To activate the Golden Fever, you will need to use Wizard Wands. Wizard Wands are available once a day in the event tab. The current number of wands you have is displayed in the top right hand corner. Wizard Wands cannot be obtained through attacks, nor can they be purchased with orbs.

When you activate the Golden Fever in the event tab, you will see the gems you can find during the attacks. While it is active, you will find more valuable gems in most of the dungeons you attack. You will also be able to find gems that were not displayed in the event tab.

The time until the Golden Fever ends is displayed in the event tab and in the top right corner during attacks.

While the Golden Fever is still active, you can use Wizard Wand to prolong its effect.

After the activation of the Golden Fever ends, everything returns to normal, and the chance to find golden gems and more valuable gems returns to usual. 

Golden Fever needs to recharge before it can be activated again. You can reduce the recharge time by using Wizard Wands.