Quests:Dun Barethsol:Endhelm's Endgame

If Marcella is trying to complete The Catseyes quest, her goal will be to capture Alek and deliver him to Kord Blackhammer.

If she is trying to complete The Yetin Spirit quest, she will either capture Alek and deliver him for trial to the Wyvern Guard, kill him, or lose to him and led him lead her through the swamp.

If she is trying to help the Society of the Blade, she can begin the confrontation by trying to rob him. Once the fight starts, she can kill him or capture him and deliver him to the Society for ransom.

The key to the Endgame quests is really that Marcella will complete them somehow. The real question is how she completes them and what other quests will be completed in the process.