As others have already said just hand it to Tilbok Furrunner in Katta Castellum to recharge this item. Once you hand it to him you get the following text:-
Tilbok Furrunner says 'I see you've spoken with Condor, and no doubt he told you I can recharge this for you. Well, it's true, but don't go around telling everyone. It's not something I like to make public, you know. Keep up the good work, though, we all appreciate it around here.'
You gain party experience!!
Also a slight correction to the Item description found above. The Mask of Espionage isn't actually found in the Twilight Sea. It is the result of a quest called "Traitor to the Validus Custodus" which starts with an NPC called Legionnaire Halle in the Twilight Sea zone. The vast majority of the quest takes place in Katta Castellum.
Edited, Jan 18th 2011 8:45am by TorrinTook