Inconvenient Suitcase

The suitcase itself appears fairly ordinary from the outside: faux dragon leather, dyed an ordinary dark brown, with a pair of combination locked latches to either side of the sturdy handle and a separate hidden keyed latch in the center.   Upon opening the suitcase it, too, appears ordinary. A simple fabric covers the wood frame, with a simple pocket in the lid to allow additional storage of documents. Peeling back the fabric liner reveals a series of runes scratched into the wood of the frame, rough and hesitant as if results of a practice lesson in enchantment.   It is only when attempting to store items in the suitcase that its true nature is revealed to those without a firm grasp on the carved runes. The suitcase seems to slowly expand to allow the storage of any item placed within, provided it can pass through the opening of the case. The bottom continues to sink downward within as the case is filled, without any apparent change to the outer casing. Everything placed within the case fits, easily and neatly, with no straining to close the latches.   Attempts to move the suitcase afterwards reveal a second truth, as the case become heavier than its contents. Twice as heavy, in fact. Rune mastery is a delicate art, and this inconvenient suitcase stands witness to a student's valuable lesson on attention to detail.