Whether you are a Dreamer or The Darkness, there is one substance in Dare to Dream more precious than any other: Sand. This Sand is magical stuff and powers the abilities of both light and dark, slipping through the fingers of both sides in a never ending cycle.
At the start of a game of Dare to Dream, The Dreamers have all of the Sand. Many Guardians, Items, and Wards require Sand to be spent in order to activate their abilities. Many Actions also have a Sand cost, as indicated by the number in the diamond on the Action card. As the Dreamers spend their Sand to activate these abilities though, it flows to The Darkness.
As Sand flows to The Darkness it may be used to make many Monsters more dangerous, or to power powerful Darkness Actions. Many of The Darkness' weaker Actions can have their effects canceled, but only if the Dreamers are willing to let more of their precious Sand slip from their hands to The Darkness. The Darkness also possesses a few Actions which are much more expensive than the Dreamers Actions, but are also much more powerful.
Sand spent by The Darkness is neither lost forever nor returned to the Dreamers, but simply returned to the Sand Box, from which the Dreamers can hope to reclaim it and put it back to use again.
The Dreamers cannot hope to win without spending some Sand, but must be careful not to give The Darkness too much or they risk getting overwhelmed. The Darkness similarly must choose between trying to horde Sand for powerful Actions later, or use their Sand now for the chance at a quick victory.