Possibly a slightly tongue-in-cheek query. I'm revisiting Passage through Mirkwood. Ungoliant's Spawn was first card out of the encounter deck. When I got to stage 3B, I got "Don't Leave the Path" - have I already fulfilled the condition "The players must find and defeat Ungoliant's Spawn to win this game" ?

I refer you to this discussion: https://community.fantasyflightgames.com/topic/233501-ungoliant-spawn-in-the-victory-display/

In summary, you need to find him again and kill him again, which is sometimes difficult.

If you don't want to kill Ungoliant's Spawn twice I believe it is valid to keep it engaged with you until you reach stage 3B. For example trap it in a Forest Snare then kill it during the last quest stage.

Thanks guys - you've confirmed my suspicions. In the game, I actually did do what jnicol suggested, and hold off killing the Spawn until stage 3 (just in case I drew "Don't leave the Path"). It did cost me in defenders, not having a trap in my deck. I was just hoping for an easier option - foolish me!