a container to hold aether
If destroyed while full of aether, deals 1dFUCKALLHELLBREAKSLOOSE to the carrier and probably everyone nearby, and probably the next 13 generations of everyone nearby, and everyone who walks past nearby, until forever.
A focus is a magical implement. Created to store one measure of aether it removes the need to fight the energy stored within. These are not rare items, and most mages are able to come by them for not too high a price. In Dansorg, they have rumored to create fantastical foci that can store multiple measures or measures of multiple planets. As long as the mage has time to meditate for the alloted number of minutes, there is no other difficulty drawing the aether into the focus.