Granite cube: A granite cube looks like an 8-inch block of grey stone with smooth sides.  Typically, the command word will be chiseled into one of the faces.  When the command word is spoken, the block begins enlarging at a (relatively) slow rate until it reaches its full size of 10 ft. by 10 ft. by 10 ft.  It takes an entire round for the block to grow.  Once full size, the granite cube is no longer magical.
Caster Level: 5th; Prerequisites: Craft Wondrous Item, shrink item; Market Price: 750 gp; Weight: 1 lb.

Source: “Stairway of Desolation” from The Infinite Staircase
Converted by Kajal, the Southern Oracle