It really depends on your playstyle. And the difficulty level. If you're on Tactician for example, there are fewer viable options because the enemies have 30% more hp and +2 to attack rolls etc, meaning if you don't have advantage or a chokepoint, you'd have to potentially 'cheese' the game. This response involves 'not' cheesing it on Tactician so lower difficulty levels open themselves up for more options. One long rest and two short rests should get you through all three.
- So when you go through the goblin camp and the big double doors, you're greeted with a hallway with some goblins talking. Flanking either side of this hall is a high ground terrace. Get your characters up there on one side. Then initiate combat, unalive the goblins on the same terrace as you are, and use grease on the base of the ladder and path leading to the ladder. Your goal is to own as much of the turn economy as possible and goblins playing slip'n'slide on grease reduces the number of hostile responses to your actions. You have the high ground and just hit the goblins from the safety advantage provides you.
- At this point, you'll just have cleared some grunts. Now Priestess Gut is further down the hallway, where you'll now have a series of stone columns on either side. Move a couple party members to either side and then create an illusion or do something to bring the goblins closest to your position into initiative.
- Use the columns, run out, cast a spell, shoot an arrow, then hide. Use grease here as well to minimize their ability to dash over to you. Any goblins who 'save' on the grease should be priority over the prone ones.
- Gut will join this fight and you've funneled them all into this corridor so just wear them down.
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- For Minthara, there's a huge double door that leads to Dror on the right of Dror's room. Don't open that door, but keep your folks in front of it and do the same thing you did with the columns earlier. Minthara's room is to the immediate right of Dror's and Dror's troops won't aggro as long as his doors remain closed during the Minthara fight and you don't show yourself through the holes in the wall when the guards are pacing in Dror's room. Run out of cover, long shot into Minthara's room, then hide. Hit the closest goblins/Minthara on back. Also you can ignore the 'Eye' here
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- For Dror, go back downstairs first and open the dungeon cage door. There's a couple spiders in there.
- Using potion of animal speaking (or a spell of the same), convince them to attack the goblins. You want to do this after you've cleared everything up to Dror's door (not inside) but the random sentries outside Dror's room, or the spiders' AI gets stuck in their cell with those goblin archers shooting down at them
- The spiders will run up the stairs and are good cannon fodder for you when you open Dror's door. They also blind goblin casters
- When the fight starts, Dror is the problem due to his AOE buffs for the rest of the grunts
- Keep your folks in cover as much as you can from the ranged enemies as Dror will come right out to attack you in melee. If you can engage Dror while in cover from the ranged enemies, that's where you'll have the fastest takedown. And again the spiders will provide a good distraction. Dror will rock their world but the grunts will take a couple turns to out them. If you can keep Dror focused on you and not the spiders that is.
And that's it. Of course all of this is even easier if you have Halsin with you.