Why won’t the Boethiah cultist die?

Question

On PS4, I started the Boethiah’s Calling quest at level 27 and killed all of the cultists except one. This one, in particular, won’t take damage and knocks my follower every time I try to go to the pillar. I gave up and did other quests. I’m now level 43 and the cultist still doesn’t take any damage.

Answer 1

As per the UESP Wiki article on Boethiah's Calling:

If you kill the priestess before talking to Boethiah, one or two of the current fighters may become unkillable.

You'd have to load a save where the priestess hasn't been killed yet. And then don't kill her before talking to Boethiah.

If playing on the PC, you can use console commands to fix the issue:

Open the console and for each fighter that's unkillable, click on them and then type kill. The quest will proceed as normal once all the fighters are dead. If that does not work, open the console and type damageactorvalue health 500.

Answer 2

Since you cant use console commands, I found that you can potentially bypass this issue by carefully sneaking aroung back from the mountains to the right. Sneakily sacrifice a follower (by making them interact with the pole) and kill them with the sacrificial knife. Hurry the conversation, he may aggro, but after she says to fight, he should be damagable again.

If this doesnt help now, hopefully it can help future sons of Skyrim.

Answer 3

The answer by user272187 works like a charm, I will contribute with more details on how to apply it.

I had the exact same issue as the OP and to make things worse I was using a mage build, so the cultist could kill me in about 3 hits making it very hard to not get killed while talking to Boethiah.

The steps are:

1. Quicksave before reaching the Sacellum of Boethiah so you can retry the steps in case something goes wrong.
2. Sneak through the rocks on the right side of the area and reach the bottom of the altar next to a tent.
3. Hug the wall at the bottom of the altar to reach the steps without being heard/seen.
4. Make the follower interact with the pillar of sacrifice.
5. When the follower is trapped go down the steps and summon one or more creatures to distract the Cultist and give you more time to finish the conversation.
6. Kill the follower (any death will do, no need for the sacrificial dagger).

As soon as the conversation starts the cultist becomes mortal and depending on the summoned creature(s) they may even kill the cultist for you.

In my case, I summoned 2 Dremora Lords and they killed the cultist even before I could reply to Boethiah, making the quest automatically skip from Find the cult of Boethiah to Speak to Boethiah's Conduit

After that you should be able to finish the quest without problems.

Extra tips:

• If you have low sneak you can increase the chances of not being detected by using the invisibility and muffle spells (alternatively, invisibility potion and boot with muffle)
• By setting the quest as active you can see the cultist on the compass at all times as the Find the cult of Boethiah objective points to him.
• If you don't have conjuration spells you can use scrolls.
• Should be obvious, but don't summon any creature before the follower is trapped by the pillar otherwise they will attack the cultist and you will have to restart the process.

This saved my platinum trophy on the PS4 as the Ebony Mail is required for the Oblivion Walker achievement.