Some items (specifically powders) can be used to feed the mysterious puzzle box and Ecofuel Flamethrower items. This page documents the items that can be fed to them.
† Grinding red flakes, leaving them in the mysterious puzzle box's powder pouring chamber over rollover, and then grinding them again before opening the chamber yields blood of the ancients. Otherwise, you receive red dust.
Unsurprisingly, items are not 'stored' inside the puzzle box between resets. Also, if you have more than one box, if you put something in one box, and open up another box, it will in there. Kinak hinted that the chamber is not actually in the box, but in fact some kind of unearthly-dimension-portal that all boxes lead to.
History
Before July 7, 2010 adding an item to the pouring chamber gave a special message. Those messages were: