I assume you're referring to Soulsinger's Soulsword, which is a wand/sword that does 100 Death damage. Of course, it's No Auction.
I haven't heard anything about it being retired from the game, so I would assume that it's still available.
Mr. Soulsinger is known to drop well over 40 different items. That would mean that the chances of getting any one particular one would probably be less than 4%, or less often than 1 in 25, although he probably drops some things more often than others. That means that you could get 3 in the next 10 battles, or none in the next 150 battles.
If you can't get a definite answer on this, and you don't want to spend a long time farming, you might go to the Bazaar and get the Blade of Ashes or Grimcaster's Blade of Severity, each of which does 95 Death damage.