WoWDB

Ancient Amber is a rare solve from the Fossil branch of Archaeology.  It requires 100 x  Fossil Archaeology Fragment.  There is no keystone for this branch that you may use to reach the needed number of fragments, so you will need to farm all 100.

Using the amber will shrink the size of your character and stun it.  It will not protect you from damage.  To remove the buff before the five minute duration is up, right-click its icon on your player frame; or open chat and type (not including the quote marks) "/cancelaura trapped in amber".

In Warlords of Draenor, this item will be added to the new Toy Box feature and no longer take up space in a character's inventory.  You will be able to "use" the item straight from the Toy Box interface.  The Toy Box will be account-wide and therefore so will this item.