Baldur's Gate III - Spoiler Edition (please read updated OP)

You just have to put on the mask to go through the door, but because you get possessed pretty fast you have to put it on right in front of the door to save time. Once you're through you can then go into your equipment to take the mask off after possession, then all will be well again.

It's an illusion, you can walk right through it without the mask. But keep the mask. After you deal with the hag, there is a 2nd hidden area, just past the masked enemies, through the waterfall and to the right. It'll require a jump to get to, but you'll need the mask to get through that door. I'll let you discover the rest.

oh are you taking about the illusion behind the fireplace? if so I got through that just fine, I was talking about the living door in her torture den? I killed the hag after I got past the waterfall and not in her hut.

oh I eventually found that area too, took a while but I still had to use the mask to walk through the illusion door there as well in order to get to the teleport. Without the mask my character seemed to just be walking into a wall. So you didn't have to use the mask to walk through any of the illusions at all?! My PC is jealous 

However I was actually referring to the door that was in the room right before you get to the enemies and the waterfall, the one in the room with the petrified dwarf and tortured elf, sorry if I was unclear. I think that was the one reznore was talking about but I'm unsure.

No door illusion would let my character pass through without the mask for some reason, so I had to constantly put it on and take it off every time I found a door. :/

OMG I just spent like THREE hours trying to kill Ethel...holy $^%$# how do people do it without shoving her off the cliff??!! I swear that entire fight is broken and you'd have to have some extremely lucky odds to get her with her loot.

Her masks seemed bugged for me too..I turned into her minion almost immediately without getting a chance to take it off, so I ended up running my way through those noxious clouds bringing my party down to half health. xD

Then I tried brute force drawing her out. That clearly doesn't work so I then used stealth to position my party in all four corners of the area and used psionic pull to get Mayrina out of the cage at the start of the battle.

I managed to get her down to 10 health a few times before she tried to persuade me to spare her for extra power, which I refused because I wanted her trinkets lol.

The thing that kills this battle is the last phase where she uses her illusion trick again when everyone's exhausted and out of spells. Her illusions just keep continuously attacking you with acid blasts and hold position(which is the real fight winner) which barely allows me a chance to counterattack. In the end I ended up shoving her off a cliff to progress which straight up annoyed me.

I did manage to clear out the entire goblin camp though, the trick is to enter from the front and bottleneck them with fire and acid spells. Gale chose a good time to die because his necrosis killed off a few goblins for me and I got his creepy resurrection quest.

Also I am amazed at how much stuff is in the game already...I thought the celebration with the druids would be the end of the act but there's more. The amount of work that's already gone into this game blows my mind...like there's just so much dialogue and clearly a lot of thought put into each encounter. I love that in almost every main conversation you can relate it back to your character's origin. This game is so worth the asking price, imo even in early access the quality of this game surpasses most other games in the same genre.

Yeah that entire fight was a headache and twice when I got her down to half health the game froze but it's to be expected. She wasn't all that hard when she didn't have her illusions up so I always made sure I attacked them first just to get rid of them, even when I knew which one was the real hag. I didn't know you could push her off the cliff though, would've save me a lot of trouble. :/