I haven't started Attack on Mournhold, and I can see no other reason for why the quest wont start. I got the message as I entered the tomb, but no journal entry, and even if I can get Mehra to say the relevant latest rumour, the conversation topic that initiates the next part of the quest doesn't show up. I'd use setstage but I'm not sure of the quest ID. Please help!
I gave it a try but without
I gave it a try but without success. Thanks for trying, though!
You have to wait for three
You have to wait for three days after starting the quest in the tomb. After that talk to Nerile Andaren or Mehra Helas. Please don't use console commands as this will break the quest.
I went off to Solstheim
I went off to Solstheim anyway and now that main quest is broken because no Good Beast shows up and it's impossible to loot the lightkeeper, thus breaking both quests.
I only use console codes as a last resort (especially in morroblivion because they are nigh impossible to get hold of) when all other avenues are exhausted.

Try talking to Nerile Andaren
Try talking to Nerile Andaren at Mournhold Temple to see if Quest Picks up.