My initial thought on this is yes but here goes.

Thalin is committed to quest during phase 2 of Journey Down the Anduin; after we resolve questing we have 15 of 16 progress tokens on the quest. During combat, Legolas kills an enemy, producing 2 more progress tokens and moving us on to stage 3, the Ambush.

While revealing the 4 cards for the Ambush we draw 1 location, 1 treachery and 2 Crows. Does Thalin`s ability still trigger at this point, thereby wiping out the crows? There were no other enemies in play so this would give us a quick win on stage 3.

He was committed to the quest and the Crows were revealed from the Encounter Deck; there is nothing on Thalin`s card to specify which phase of the turn he does or doesn`t apply to.

Assuming the answer to this question is yes,how do we feel about Thalin`s ability entering the last stage of Journey through Mirkwood; for instance if you have to pull Ungoliant`s Spawn out of the encounter discard pile, does Thalin still damage him?

Many apologies if this has already been covered, I read the posts about Thalin vs. Surge but didn`t find anything on these scenarios.

 A character is committed to the quest only in the quest phase. Rulebook page 14.

Thanks, after re-reading pg. 14 that makes more sense.

 So that means you would win, right? You revealed stage 3 during the quest phase -- you hadn't moved on to the travel phase yet -- so the crows would be taken out by Thalin's ability. It lasts through the quest phase, not just the staging step of the quest phase.

 Take another look at the example - Stage 3 was revealed during the Combat phase thanks to Legolas.

 Whoops. Missed that. Thanks.