Sand of Hours
From Zelda Wiki.org
The Sand of Hours is an integral part of Phantom Hourglass. They provide the power for the Phantom Hourglass itself, allowing the one who holds it to penetrate further into the Temple of the Ocean King. When Link first gets the Phantom Hourglass, it comes with 10 minutes worth of time. Most of the bosses provide more Sand for the Hourglass upon defeat, enough for two extra minutes worth of time. In addition, five treasures at sea hold one minute's worth of time.
Time spent inside of the Temple of the Ocean King depletes minutes from the Phantom Hourglass. It is recharged instantly by the sun when outside the temple. Safe Zones however, do not deplete time from the Phantom Hourglass.
Additional temporary time upgrades can be found throughout the temple. These will not add to the total Sands of Hours.
Spoiler warning: The following contains key plot or ending details.
The Sand of Hours is the source of power for the Ocean King, as well. In addition, they are the crystallized form of the Life Force, which the game's antagonist, Bellum, consumes.
