Ran Lines of Supply. Killed all the convoys and got the following message:
(Dungeon Master): You've eliminated every Supply convoy! Not a single one made it through to the Netherese army! Kyra Armond has another chest waiting for you back at her camp.

Only chest I have come across is the one for killing the General after taking out the convoys. No other chest at her camp of the Harper Trap makers camp either. The word "another" would imply more than one.

Only ran it on Heroic so far. Does a second chest drop on Epic level runs?