When placed on the Portal of Power, the item slows down time for everything other than the Skylander. It lasts for about 45 seconds per chapter. The figure can be removed from the portal to save part of the duration for later. When changing or resetting chapters, the hourglass’ duration recharges to full.
To use the hourglass in the 3DS version, it first needs to be added to the game by Wendel in the same way a Skylander would be added. It will then be stored under the R button, which the player can press to activate it. While active, the hourglass will paralzye nearby enemies. Each activation costs 10 radiance.
At the moment, the hourglass doesn’t do anything other than expanding the collection and counting towards the Collector medal.