The dungeon only really has one fight in it, which you can avoid if you want to; the rest is more of an atmospheric experience, which is pretty neat.
The enemies in the encounter have broken cheaty abilities that stand outside 5e rules considerably, and the current issues with the implementation of status effects (prone and fear in particular) make those abilities particularly egregious. For that fight, I'd recommend (if you're intending to do it fairly and not abuse larianisms for an easy win), employ some CC on the heavy hitter, or just keep away from him. The healer should go down in one or two shots as soon as you can spare them. Try not to group your party members up, since their 'special' abilities are AoEs that can debilitate your whole party.
For Ethel herself, the biggest tip I have to offer is this: Mark her. Hunter's mark (if you'll be playing a ranger as you say), Hex, or some other lasting effect that you can stick on her will mean that you can see which one she is when she duplicates herself. It won't stop the clones from messing with you, but it means you won't waste shots. Multi-hit spells, like magic missile are also excellent for taking out clones quickly and easily. The second time she splits up, you'll notice that none of the clones are marked: Ether herself turned invisible in the same action, and is not any of them. If you don't want to cheat or exploit, but you have access to faerie fire, you can ping her with it before she splits the second time ,and deny her ability to hide - or you can guess where she is and try to catch her in it after she splits. Elsewise, just wait for her to reveal herself again, and knock out the clones in the mean time.
If you skip the fight above, Ethel will summon the masks to help her - knocking them unconscious first, alone, will prevent them joining the fight.
To save Mayrina, you just have to get someone to the switch and hit it before the cage burns. This can be a matter of luck if the damage Ethel does on her first freebie strike goes badly - she can do a little, or a lot to the cage on the first hit, and that can swing it. If you've got an Astarion or other rogue who can dash three or even four times, you can reach the button right away. If you've got a halfling in your party, you can throw them to the button, though it'll hurt the character a little if you do so. Alternatively, if you're a druid, use alight wild shape (cat for example), and have someone throw that - you'll turn back immediately when you hit the ground, from damage, and be able to hit the button on your turn.
Last edited by Niara; 13/07/21 08:15 AM.