Guild Wars: Getting the Tengu Mask
Also note that the Tengu event has been extended if you register your pre-order key by the end of today (i.e. 23:59 PST). Assuming you register in time, you can play the event till 23:59 PST, May 2. Seems likely this was done because a bunch of Collector's Editions of GW: Factions didn't ship in time.
Update: Apparently I was wrong. The Day of the Tengu event is now over, according to the game updates page. Seems that they just meant that pre-order customers can play Factions a bit longer if they activate the key. Shame they didn't make that clearer.