This quest is not available in game.
Seek out Gregan Brewspewer in northern Feralas. From him, learn how you may acquire the Videre Elixir, then return to Donova Snowden in Winterspring.
Now, what's this? Linken... FORGOT?
Oh, I see... Lost his memory...
Well, here is his sword. It's not complete, though. I know of the one that can finish it, but... speaking with him may prove difficult.
Listen, I know of someone that will be able to help you. It's too much to explain right now, but you must somehow acquire a Videre Elixir. The only one I know that can help you with that is Gregan Brewspewer. He's hard to track down, but last I knew he was camping in the wilds of Feralas.