From Dulfy:
The old Halloween weapons such as Greatsaw Greatsword, Ghastly Grinning Shield etc are now obtainable as a random drop when you combine weapons in the Mystic Forge. Anet developer, "This is part of some updates that I’ve been working on with the mystic forge, though we had not intended it to go out with last weeks build, as some parts of the change still need some work. I didn’t put this in the update notes since it wasn’t meant to go live yet, but since it apparently went through, we added the Bloodbound weapons, Shadow of the Mad King weapons, and some weapons with no way to get them anymore like Scarlet’s Kiss to the mystic forge as possible rewards for combining rare weapons."

Read More:
http://dulfy.net/2016/04/25/gw2-halloween-and-other-weapons-available-via-mystic-forge/