Umbra isn't that strong, Goldbrand and Hatred's Hearth are better, so get the mask. Oh and help the Jemane brothers and wait in Chorrol for a few days and you will get a quest to obtain a good sword called the Honorblade of Chorrol and if you bring it back to the Count of Chorrol you will get the Estruchen of Chorrol wich is a shield that gives reflect damage and you can steal the Honorblade back from the countess.
danju, i have less respect for you now, get the mask? the sword is worth it, even if there are better ones