Hrm - this sounds like I should speed up importing the quests to the wiki.
The videos you watched were out of date - in Update 2, the board is no longer in the Midnight Forum, but rather located on various levels of the dungeons.
If I remember right, “The Saurean’s challenge” is (I think) a completely removed quest in Update 2. It was for a section of caves that you went through before reaching Marcaul, which were removed in the update. On stepping through a portal to the Marcaul outskirts, you should have been been given the quest “Enter Marcaul”, which should have completed once you jumped over the gate; eventually, you should get a key of Haprukala which lets you go down the spiral stairs around her, and venture into deeper levels of the Underworld.
Did you have a save where you were doing the Saurian’s challenge from some time ago, which you loaded after Update 2? If so, I’m not sure this was tested for the update, and it could cause this problem. The best solution might be to restart - which is worth doing, if that was the case, as the intro has been significantly shortened and improved in the update.
If that’s not what caused it, but the Saurean’s Challenge is still the quest I’m thinking of, then I suspect that if you upload your save file someone should be able to fix it for ya.